# Math riddles hard

## Math Riddles: Easy, Hard, Tricky

Test your knowledge with these math riddles and brain teasers. You’ll find easy riddles and math puzzlers suitable for kids. For those looking for a greater challenge, take on the difficult math riddles below.

Educators use math story problems to enhance understanding and visualization for their students. These math riddles with answers are a fun way to test your ability to solve math problems.

### Math Riddles for Kids

Here we go.

1.) If two’s company and three’s a crowd, what are four and five?
Nine.

2.) If you multiply this number by any other number, the answer will always be the same. What number is this?
Zero.

3.) A duck was given $9. A spider was given$36. A bee was given $27. Based on this information, how much money would be given to a cat?$18 ($4.50 per leg). 4.) A grandfather, two fathers, and two sons went to the movie theater together, and everyone bought one movie ticket each. How many tickets did they buy in total? Three (the grandfather is also a father and the father is also a son). 5.) A little boy goes shopping and purchases 12 tomatoes. On the way home, all but 9 get mushed and ruined. How many tomatoes are left in good condition? Nine tomatoes. ### For Middle Schoolers We’re raising the ante. Put on your thinking caps for a logic puzzle direction that incorporates math. What occurs twice in a week, once in a year but never in a day? The letter E. If there are 4 apples and you take away 3, how many do you have? Three apples. If the zookeeper had 100 pairs of animals in her zoo and two pairs of babies are born for each original animal, then sadly, 23 animals don’t survive. How many animals do you have left in total? 977 animals (100×2 = 200; 200+800 = 1000; 1000-23 = 977). ### Tricky Math Riddles and Brain Games Eggs are$0.12 a dozen. How many eggs can you get for a dollar?
100 eggs (one penny each).

In an alien land far away, half of 10 is 6. If the same proportion holds, then what is 1/6th of 30 in this alien land?
6.

Scott has $28.75. He purchased three cookies that cost$1.50 each, five newspapers that each cost $0.50, five flowers for$1.25 each, and used the remainder of the cash on a pair of sunglasses. How much were the sunglasses?
$15.50. ### Easy Puzzles Which month has 28 days? All of them, of course! What 4 days of the week start with the letter T? Tuesday, Thursday, Today, and Tomorrow. What goes up and doesn’t come back down? Your age. A cell phone and phone case cost$110 in total. The cell phone costs $100 more than the phone case. How much was the cell phone?$105 (not $110). What has a thumb and four fingers but is not alive? A glove. What occurs once every minute, twice in every moment, and yet never in a thousand years? The letter M. ### Number Math Riddles I am an odd number; take away an alphabet, and I become even. What number am I? Seven (SEVEN-S=EVEN). Using only addition, how can you add eight 8’s to get the number 1,000? 888 +88 +8 +8 +8 =1,000. How did the soccer fan know before the game that the score would be 0-0? The score is always 0-0 before the game. I add five to nine and get two. The answer is correct, but how? When it is 9 am, add 5 hours to it, and you will get 2 pm. The ages of a father and son add up to 66. The father’s age is the son’s age reversed. How old could they be? Three possible answers: the father-son duo could be 51 and 15 years old, 42 and 24 years old, or 60 and 06 years old. A merchant can place eight large boxes or 10 small boxes into a carton for shipping. In one shipment, the shipper sent a total of 96 boxes. If there are more large boxes than small boxes, how many cartons did the shipper ship? 11 cartons total. Seven large boxes (7 x 8 = 56 boxes) and four small boxes (4 x 10 = 40). My sister lives at the reverse of my house number. The difference between our house numbers ends in two. What are the lowest possible numbers for our house? 19 and 91. ### Funny Math Riddles Where do fish keep their money? In the river bank. If you buy a rooster to lay eggs and expect to get three eggs each day for breakfast, how many eggs will you have after three weeks? None, roosters do not lay eggs. I am an odd number. Take away a letter, and I become even. What number am I? Seven. I am a place, in a state. I am an answer to a math problem. The math problem is: To get a cube, you multiply something by 6. What do you multiply by? You Times Square! What weighs more, a pound of iron or a pound of feathers? Both would weigh the same. When asked how old she was, Janey replied, “In two years, I will be twice as old as I was five years ago.” How old is she? She’s 12. ### Puzzles Ready for some serious problem-solving? How can you make the following equation true by drawing only one straight line: 5+5+5=550? Can you figure it out? Draw a line on the first plus sign that turns it into a 4! The equation then becomes true: 545+5=550. You could also change the equal symbol to a crossed-out equal symbol which means “not equal to.” A certain number has three digits. The sum of the three digits equals 36 times this number. Seven times the left digit plus 9 equals 5 times the sum of the two other digits. 8 times the second digit minus 9 is equal to the sum of the first and third. What is the number? 324. Can you arrange four nines to make it equal to 100? 99+9/9 = 100. Caleb is 54 years old, and his father Franklin is 80. How many years ago was Franklin three times the age of his son Caleb? 41 years ago. The day before yesterday, I was 21, and the next year I will be 24. What day is my birthday? 31st December. It must be on the 1st of January when I turned 22 and so 21 the day before. As it is now a new year, I will be 23 this year and 24 next year. If it were two hours later, it would be half as long until midnight as it would be if it were an hour later. What time is it now? 9 pm. There are several books on a bookshelf. How many books are on the shelf if one book is the 4th from the left and the 6th from the right? 9 books. ### Good Math Riddles What’s the easiest way to double your money? Put it in front of a mirror. If two’s company and three’s a crowd, what are four and five? Four and five = nine. Adored by few, Feared and hated by many. Mistress of the entire universal reason, Master in the art of numbers. Some may have solved many of your mysteries, But there are still many of them to find. What are they? Mathematics. Two fathers and two sons go fishing. Each of them catches one fish. So why do they bring home only three fish? Because the fishing group consists of a grandfather, his son, and his son’s son. What has a face and two hands but no arms or legs? A clock. If it took 6 people 9 hours to build a barn, how long would it take 12 people to build the same barn? None, the barn is already built. One brother said of his younger brother, “Two years ago, I was three times as old as my brother. In three years, I will be twice as old as my brother.” How old are each of the brothers now? The older brother is 17 years old, and the younger brother is 7. ### Hard Ones One out of 9 otherwise identical balls is overweight. How can it be identified after 2 weighings? Weigh a group of 3 balls against another group of 3. Then you’ll know which group of 3 contains the heavy ball. Pick 2 balls from that group and weigh one against the other. A nonstop train leaves Moscow for Leningrad at 60 mph. Another nonstop train leaves Leningrad for Moscow at 40 mph. How far apart are the trains 1 hour before they pass each other? 100 miles (60+40). I am a three-digit number. My tens digit is five more than my one’s digit. My hundreds digit is eight less than my tens digit. What number am I? 194. When my father was 31, I was 8. Now he is twice as old as me. How old am I? The age difference is 23 years, so I must be 23 if my father is twice as old as me. If seven people meet each other and each shakes hands only once, how many handshakes will there have been? 21 (most people would think there were 42 handshakes). ### Tough Math Riddles In a pond, there are some flowers with some bees hovering over them. How many flowers and bees are there if both the following statements are true: 1. If each bee lands on a flower, one bee doesn’t get a flower. 2. If two bees share each flower, there is one flower left out. 4 bees and 3 flowers. The ages of a father and son add up to 66. The father’s age is the son’s age reversed. How old could they be (there are 3 possible solutions)? 42 and 24. 51 and 15. 60 and 6. Janie’s friends were chipping in to buy her a wedding shower present. At first, 10 friends chipped in, but 2 of them dropped out. Each of the 8 had to chip in another dollar to bring the amount back up. How much money did they plan to collect?$40 (10 at $4, or 8 at$5).

There are two ducks in front of two other ducks. And, there are two ducks behind two other ducks. There are two ducks beside two other ducks. How many ducks are there?
4 ducks (in a square).

I asked a girl how old she was. She said, “In 2 years, I will be twice as old as I was 5 years ago.” How old is she?
12.

A man dies of old age on his 25th birthday. How is this possible?
He was born on February 29th.

I am a three-digit number.
My tens digit is five more than my one’s digit.
My hundreds digit is eight less than my tens digit.
What number am I?
Number 194.

A farmer has 17 sheep, and all but 9 die. How many are left?
Nine.

What 3 positive numbers give the same result when multiplied together as when added together?
1, 2, and 3.

If you can purchase 8 eggs for 26 cents, how many can you buy for a cent and a quarter?
Eight.

Three matches are sitting on a table, without adding another make for three matches four. You are not allowed to break any of the matches.
Shape the 3 matches into a roman numeral four.

Using only addition, how can you add eight 8s to get the number 1,000?
888 + 88 + 8 + 8 + 8 = 1,000.

### Math Brain Teasers

Two schoolgirls were traveling from the city to a summer cottage on an electric train. “I notice,” one of the girls said, “that the trains coming in the opposite direction pass us every 5 minutes. What do you think—how many trains arrive in the city in an hour, given equal speeds in both directions?” “Twelve, of course,” the other girl answered, “because 60 divided by 5 equals 12.” The first girl disagreed. What do you think?

If the girls had been on a standing train, the first girl’s calculations would have been correct, but their train was moving. It took 5 minutes to meet a second train, but it took the second train 5 more minutes to reach where the girls met the first train. So the time between trains is 10 minutes, not 5, and only 6 trains per hour arrive in the city.

### The Snail Problem

A snail is at the bottom of a 20 meters deep pit. Every day the snail climbs 5 meters upwards, but at night it slides 4 meters back downwards. How many days does it take before the snail reaches the top of the pit?

The snail reaches the top of the pit on the 16th day. On the first day, the snail reaches a height of 5 meters, slides down 4 meters at night, and thus ends at the height of 1 meter. And, on the second day, he reaches 6 meters but slides back to 2 meters.

On the third day, he reaches 7 meters but slides back to 3 meters. And, on the fifteenth day, he reaches 19 meters but slides back to 15 meters. On the sixteenth day, he reaches 20 meters, so now he is at the top of the pit.

### Difficult Math Puzzles Word Problems

There is a certain club which is for men only. 600 men belong to this club, and 5% of these men wear one earring. Of the other 95% membership, half wear two earrings, and the other half wear none. How many earrings are being worn in this club?

Six hundred. We know that 5% or 30 of the men are wearing one earring. Of the other 95%, or 570, we know that half are wearing two earrings and the other half none. This is the same as if they all wore one.

### Are Math Riddles Just For Nerds?

Heck no! They are for everyone who finds enjoyment in them or is interested in advancing their learning and expanding their minds.

Here are some notables who have taken an interest in math:

• Art Garfunkel
• Sergey Brin (Cofounder of Google)
• Lisa Kudrow
• Cindy Crawford
• Marie Curie
• Huey Lewis
• Danica McKellar (Winnie Cooper in The Wonder Years)

Being able to solve these riddles can help you solve other challenges in your day-to-day life. If anyone makes fun of you for liking math puzzles, those folks likely have a hard time solving the problems independently.

By Mike O’Halloran

Mike is an author, toy inventor, and publisher of Greeting Card Poet.

### Etcetera

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You might like these other riddle-related pages:

Brain Teasers

Best Riddles

Easy

Funny Riddles and Trick Questions

Good

Sours: https://www.greetingcardpoet.com/math-riddles-easy-hard-tricky/

## 12 tricky math riddles that stump even the smartest people

• Some math riddles are so challenging even the smartest people struggle to answer them.
• Below are 12 challenging puzzles that will leave you stumped.
• They require basic problem solving and tricky math — see if you can figure them out.

### 1. House number

My twin lives at the reverse of my house number. The difference between our house numbers ends in two. What are the lowest possible numbers of our house?

### 2. Egg equation

If a hen and a half lay an egg and a half in a day and a half, how many eggs will half a dozen hens lay in half a dozen days?

Answer: Two dozen. If you increase both the number of hens and the amount of time available four-fold, the number of eggs increases 16 times. 16 x 1.5 = 24. If math riddles aren't your thing, try solving these tricky detective riddles.

### 3. Card question

A small number of cards has been lost from a complete pack. If I deal among four people, three cards remain. If I deal among three people, two remain and if I deal among five people, two cards remain. How many cards are there?

### 4. Knight moves

I have a calculator that can display ten digits. How many different ten-digit numbers can I type using just the 0-9 keys once each, and moving from one keypress to the next using the knight’s move in chess? (In chess, the knight move in an L-shape — one square up and two across, two squares down and one across, two squares up and one across, and other like combinations)

Answer: You can form the numbers 5034927618 and 5038167294. You can also form their reverses: 8167294305 and 4927618305. Hence four different numbers can be made. The key point is to realize that the number must start or end on the ‘5’ key, followed/preceded by the ‘0’ key, otherwise, there is no way of using all ten keys during the route. Only 2 percent of people can solve Einstein's Riddle. Can you?

### 5. Two by two

You know 2 + 2 comes to the same as 2 x 2. Now find a set of three different whole numbers whose sum is equal to their total when multiplied.

Answer: The three different whole numbers whose sum is equal to their total when multiplied are 1, 2, and 3. Next, try to spot the image that isn't like the others in this picture.

### 6. Apple harvest

Mrs. Jones was very proud of her apple tree. One autumn, after harvesting her apples, she called her three sons together. "Here are 150 apples," she said. "I want you to take them to the market tomorrow and sell them for me." She gave Paul 15 apples, Nick 50, and Ben 85. "Your job," added Mrs. Jones, "is to sell the apples in such a way that each of you brings home the same amount of money." How do they do it?

Answer: The first buyer purchases 12 dozen apples at $1 per dozen. Paul sells him one dozen and has three apples left; Nick sells him four-dozen and has two apples left; Ben sells him seven-dozen and has one apple left. Then a second buyer comes along and buys all their remaining apples for$3 apiece. The three brothers head home with $10 each. Sours: https://www.businessinsider.com/tricky-math-riddles-only-the-smartest-people-can-figure-out-2018-5 ## 31 Hard Math Riddles (With Answers) for Future Geniuses Riddle: I am a three-digit number. My second digit is 4 times bigger than the third digit. My first digit is 3 less than my second digit. Who am I? Answer: 141 Riddle: I add five to nine, and get two. The answer is correct, but how? Answer: When it is 9am, add 5 hours to it and you will get to 2 pm. Riddle: There are 100 pairs of dogs in a zoo; pairs of babies are born for every dog. Unfortunately, 23 of the dogs have not survived. How many dogs would be left in total? Answer: 977 dogs Explanation: 100 x 2 = 200; 200 +800 = 1000; 1000-23 = 977 Riddle: A group of students were standing in the blazing sun facing due west on a march past event. The leader shouted at them: Right turn! About turn! Left turn! At the end of these commands, in which direction is the students facing now? Answer: East. (Explanation: They will turn 90 degrees in a right turn and they turn 180 degrees in an about-turn, and finally they turn 90 degrees in a left-turn. Therefore, the students are now facing east.) Riddle: A half is a third of it. What is it? Answer: 1 1/2. Riddle: At the time of shipping, Tom can place 10 small boxes or 8 large boxes into a carton. A total of 96 boxes were sent in one shipment. The number of small boxes was less than large boxes. What is the total number of cartons he shipped? Answer: 11 cartons (Explanation: 4 small boxes (410 = 40 boxes) + 7 large boxes (78 = 56 boxes). So, 96 boxes and 11 total cartons.) Riddle: When Miguel was 6 years old, his little sister, Leila, was half is age. If Miguel is 40 years old today, how old is Leila? Answer: She is 37 years old. Riddle: You are given 3 positive numbers. You can add these numbers and multiply them together. The result you get will be the same. Which are the numbers? Answer: 1, 2, and 3 Riddle: If a hen and a half lay an egg and a half in a day and a half, how many eggs will half a dozen hens lay in half a dozen days?Answer: 2 dozen. Riddle: What can you put between a 7 and an 8 so that the result is greater than a seven, but less than an eight? Answer: A decimal. 7.8 is greater than 7, but less than 8 Riddle: Tom was asked to paint the numbers outside 100 apartments which means he will have to paint numbers 1 through 100. Can you figure out the number of times he will have to paint the number 8? Answer: 20 times (8, 18, 28, 38, 48, 58, 68, 78, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 98) Riddle: What’s the maximum number of times you can subtract number 5 from 25? Answer: Only once. This is because when you subtract 5 for the first time, it becomes number 20, and then 15, and so on. Riddle: Which weighs more 16 ounces of soda or a pound of solid gold? Answer: Neither. They both weigh the same! Riddle: Leon works at the aquarium. When he tries to put each turtle in its own tank, he has one turtle too many. But if he puts two turtles per tank, he has on tank too many. How many turtles and how many tanks does Leon have? Answer: He has 3 tanks and 4 turtles. Riddle: The total cost of a pair of shoes and a hoodie is$150. The hoodie costs $100 more than the pair of shoes does. How much does each item cost? Answer: The hoodie costs$125, the shoes costs $25 Riddle: You have two U.S coins whose total value is$0.30. One of them is not a nickel. What are the two coins?
Answer: One is a quarter and one is a nickel.

Riddle: Eggs are $0.12 a dozen. How many eggs can you get for a dollar? Answer: 100 eggs, at a penny each. Riddle: A duck was given$9, a spider was given $36, a bee was given$27. Based on this information, how much money would be given to a cat?
Answer: $18 ($4.50 per leg)

Riddle: “How much is this bag of potatoes?” asked the man. “32 pounds divided by half of its own weight,” said the grocer. How much did the potatoes weigh?

Riddle: I am a three-digit number. My tens digit is six more than my ones digit. My hundreds digit is eight less than my tens digit. What number am I?

Riddle: A man is twice as old as his little sister. He is also half as old as his dad. Over a period of 50 years, the age of his sister will become half of their dad’s age. What is the age of the man now?

Riddle: How can you add eight 4s together so that the total adds up to 500?
Answer: 444 + 44 + 4 + 4 + 4= 500

Riddle: If seven people meet each other and each shake hands only once with each of the others, how many handshakes will there have been?

Riddle:If four men can build four tables in four hours, how many tables can eight men build in eight hours?

Riddle: When Lisa was 6 years old, her sister Lucy was half her age. If Lucy is 40 years old today, how old is Lucy?
Explanation: Lucy is 3 years younger than Lisa.

Riddle: If you buy a rooster for the purpose of laying eggs and you expect to get three eggs each day for breakfast, how many eggs will you have after three weeks?
Answer: None. Roosters don’t lay eggs.

Riddle: A farmer has 19 sheep on his land. One day, a big storm hits, and all but seven run away. How many sheep does the farmer have left?
Answer: Seven. All but seven ran away.

Who says mind-bending logic puzzles are just for kids? We've come up with 20 brand-new riddles for adults to test your critical thinking, mathematics, and logic skills. With difficulties ranging from easy, to moderate, to hard, there's something here for everyone.

So go grab a pencil and a piece of scratch paper and prepare to rip your hair out (and we really do mean that in the best way possible). When you think you've got the right answer, click the link at the bottom of each riddle to find the solution. Got it wrong? No worries, you have 19 other riddles to test out.

### Riddle #1: The King’s Orders Make for One Hell of a Brain Teaser

(Difficulty: Easy)

King Nupe of the kingdom Catan dotes on his two daughters so much that he decides the kingdom would be better off with more girls than boys, and he makes the following decree: All child-bearing couples must continue to bear children until they have a daughter!

But to avoid overpopulation, he makes an additional decree: All child-bearing couples will stop having children once they have a daughter! His subjects immediately begin following his orders.

After many years, what’s the expected ratio of girls to boys in Catan?

#### Hint

The likelihood of each baby born being a girl is, of course, 50 percent.

### Riddle #2: How Many Eggs Does This Hen Lay?

(Difficulty: Easy)

This problem is in honor of my dad, Harold Feiveson. It’s due to him that I love math puzzles, and this is one of the first problems (of many) that he gave me when I was growing up.

A hen and a half lays an egg and a half in a day and a half. How many eggs does one hen lay in one day?

### Riddle #3: The Gold Chain Math Problem Is Deceptively Simple

(Difficulty: Moderate)

You’re rummaging around your great grandmother’s attic when you find five short chains each made of four gold links. It occurs to you that if you combined them all into one big loop of 20 links, you’d have an incredible necklace. So you bring it into a jeweler, who tells you the cost of making the necklace will be \$10 for each gold link that she has to break and then reseal.

How much will it cost?

### Riddle #4: Try to Solve This Pickleball Puzzle

(Difficulty: 🚨HARD🚨)

Kenny, Abby, and Ned got together for a round-robin pickleball tournament, where, as usual, the winner stays on after each game to play the person who sat out that game. At the end of their pickleball afternoon, Abby is exhausted, having played the last seven straight games. Kenny, who is less winded, tallies up the games played:

Kenny played eight games

Abby played 12 games

Ned played 14 games

Who won the fourth game against whom?

#### Hint

How many total games were played?

### Riddle #5: Our Circuit Breaker Riddle Is Pure Evil. Sorry.

(Difficulty: 🚨HARD🚨)

The circuit breaker box in your new house is in an inconvenient corner of your basement. To your chagrin, you discover none of the 100 circuit breakers is labeled, and you face the daunting prospect of matching each circuit breaker to its respective light. (Suppose each circuit breaker maps to only one light.)

To start with, you switch all 100 lights in the house to “on,” and then you head down to your basement to begin the onerous mapping process. On every trip to your basement, you can switch any number of circuit breakers on or off. You can then roam the hallways of your house to discover which lights are on and which are off.

What is the minimum number of trips you need to make to the basement to map every circuit breaker to every light?

#### Hint

The solution does not involve either switching on or off the light switches in your house or feeling how hot the lightbulbs are. You might want to try solving for the case of 10 unlabeled circuit breakers first.

### Riddle #6: Two Trains. Two Grandmas. Can You Solve This Tricky Math Riddle?

(Difficulty: Moderate)

Jesse’s two grandmothers want to see him every weekend, but they live on opposite sides of town. As a compromise, he tells them that every Sunday, he’ll head to the subway station nearest to his apartment at a random time of the day and will hop on the next train that arrives.

If it happens to be the train traveling north, he’ll visit his Grandma Erica uptown, and if it happens to be the train traveling south, he’ll visit his Grandma Cara downtown. Both of his grandmothers are okay with this plan, since they know both the northbound and southbound trains run every 20 minutes.

But after a few months of doing this, Grandma Cara complains that she sees him only one out of five Sundays. Jesse promises he’s indeed heading to the station at a random time each day. How can this be?

#### Hint

The trains always arrive at their scheduled times.

### Riddle #7: Here's a Really [email protected]*#ing Hard Math Problem About Ants

(Difficulty: 🚨HARD🚨)

Max and Rose are ant siblings. They love to race each other, but always tie, since they actually crawl at the exact same speed. So they decide to create a race where one of them (hopefully) will win.

For this race, each of them will start at the bottom corner of a cuboid, and then crawl as fast as they can to reach a crumb at the opposite corner. The measurements of their cuboids are as pictured:

Laura Feiveson

If they both take the shortest possible route to reach their crumb, who will reach their crumb first? (Don’t forget they’re ants, so of course they can climb anywhere on the edges or surface of the cuboid.)

#### Hint

Remember: Think outside the box.

### Riddle #8: This Peppermint Patty Riddle Is Practically Impossible

(Difficulty: 🚨HARD🚨)

You’re facing your friend, Caryn, in a “candy-off,” which works as follows: There’s a pile of 100 caramels and one peppermint patty. You and Caryn will go back and forth taking at least one and no more than five caramels from the candy pile in each turn. The person who removes the last caramel will also get the peppermint patty. And you love peppermint patties.

Suppose Caryn lets you decide who goes first. Who should you choose in order to make sure you win the peppermint patty?

#### Hint

First, solve for a pile of 10 caramels.

### Riddle #9: Can You Solve the Great American Rail-Trail Riddle?

(Difficulty: Moderate)

This problem was suggested by the physicist P. Jeffrey Ungar.

Finally, the Great American Rail-Trail across the whole country is complete! Go ahead, pat yourself on the back—you’ve just installed the longest handrail in the history of the world, with 4,000 miles from beginning to end. But just after the opening ceremony, your assistant reminds you that the metal you used for the handrail expands slightly in summer, so that its length will increase by one inch in total.

“Ha!” you say, “One inch in a 4,000 mile handrail? That’s nothing!” But … are you right?

Let’s suppose when the handrail expands, it buckles upward at its weakest point, which is in the center. How much higher will pedestrians in the middle of the country have to reach in summer to grab the handrail? That is, in the figure below, what is h? (For the purposes of this question, ignore the curvature of the Earth and assume the trail is a straight line.)

Laura Feiveson

#### Hint

Pythagoras is a fascinating historical figure.

### Riddle #10: This Riddle Is Like an Especially Cruel SAT Problem. Can You Find the Answer?

(Difficulty: Moderate)

Amanda lives with her teenage son, Matt, in the countryside—a car ride away from Matt’s school. Every afternoon, Amanda leaves the house at the same time, drives to the school at a constant speed, picks Matt up exactly when his chess club ends at 5 p.m., and then they immediately return home together at the same constant speed. But one day, Matt isn’t feeling well, so he leaves chess practice early and starts to head home on his portable scooter.

After Matt has been scooting for an hour, Amanda comes across him in her car (on her usual route to pick him up), and they return together, arriving home 40 minutes earlier than they usually do. How much chess practice did Matt miss?

#### Hint

Consider the case where Amanda meets Matt exactly as she’s leaving their house.

### Riddle #11: Can You Get These 3 Movie Stars Across the River?

(Difficulty: Moderate)

Three movie stars, Chloe, Lexa, and Jon, are filming a movie in the Amazon. They’re very famous and very high-maintenance, so their agents are always with them. One day, after filming a scene deep in the rainforest, the three actors and their agents decide to head back to home base by foot. Suddenly, they come to a large river.

On the riverbank, they find a small rowboat, but it’s only big enough to hold two of them at one time. The catch? None of the agents are comfortable leaving their movie star with any other agents if they’re not there as well. They don’t trust that the other agents won’t try to poach their star.

For example, Chloe’s agent is okay if Chloe and Lexa are alone in the boat or on one of the riverbanks, but definitely not okay if Lexa’s agent is also with them. So how can they all get across the river?

#### Hint

There isn’t just one way to solve this problem.

### Riddle #12: This Ludicrously Hard Riddle Is Our Tribute to a Late Math Genius. Can You Figure It Out?

(Difficulty: 🚨HARD🚨)

On April 11, John Horton Conway, a brilliant mathematician who had an intense and playful love of puzzles and games, died of complications from COVID-19. Conway is the inventor of one of my favorite legendary problems (not for the faint of heart) and, famously, the Game of Life. I created this problem in his honor.

Carol was creating a family tree, but had trouble tracking down her mother’s birthdate. The only clue she found was a letter written from her grandfather to her grandmother on the day her mother was born. Unfortunately, some of the characters were smudged out, represented here with a “___”. (The length of the line does not reflect the number of smudged characters.)

“Dear Virginia,

Little did I know when I headed to work this Monday morning, that by evening we would have a beautiful baby girl. And on our wedding anniversary, no less! It makes me think back to that incredible weekend day, J___ 27th, 19___, when we first shared our vow to create a family together, and, well, here we are! Happy eighth anniversary, my love.

Love, Edwin”

The question: When was Carol’s mother born?

#### Hint

This problem is inspired by Conway’s Doomsday Rule.

### Riddle #13: To Solve This Twisty Math Riddle, You Just Need One Belt and One Earth

(Difficulty: Moderate)

Imagine you have a very long belt. Well, extremely long, really … in fact, it’s just long enough that it can wrap snugly around the circumference of our entire planet. (For the sake of simplicity, let’s suppose Earth is perfectly round, with no mountains, oceans, or other barriers in the way of the belt.)

Naturally, you’re very proud of your belt. But then your brother, Peter, shows up—and to your disgruntlement, he produces a belt that’s just a bit longer than yours. He brags his belt is longer by exactly his height: 6 feet.

If Peter were also to wrap his belt around the circumference of Earth, how far above the surface could he suspend the belt if he pulled it tautly and uniformly?

#### Hint

Earth’s circumference is about 25,000 miles, or 130 million feet … but you don’t need to know that to solve this problem.

### Riddle #14: This Elbow Tapping Riddle Is Diabolical. Good Luck Solving It.

(Difficulty: 🚨HARD🚨)

In some future time, when the shelter-in-place bans are lifted, a married couple, Florian and Julia, head over to a bar to celebrate their newfound freedom.

They find four other couples there who had the same idea.

Eager for social contact, every person in the five couples enthusiastically taps elbows (the new handshake) with each person they haven’t yet met.

It actually turns out many of the people had known each other prior, so when Julia asks everyone how many elbows they each tapped, she remarkably gets nine different answers!

The question: How many elbows did Florian tap?

#### Hint

What nine answers did Julia hear?

### Riddle #15: You'll Need a Drink After Trying to Solve This Whisky Riddle

(Difficulty: Easy)

Alan and Claire live by the old Scottish saying, “Never have whisky without water, nor water without whisky!” So one day, when Alan has in front of him a glass of whisky, and Claire has in front of her a same-sized glass of water, Alan takes a spoonful of his whisky and puts it in Claire’s water.

Claire stirs her whisky-tinted water, and then puts a spoonful of this mixture back into Alan’s whisky to make sure they have exactly the same amount to drink.

So: Is there more water in Alan’s whisky, or more whisky in Claire’s water?And does it matter how well Claire stirred?

#### Hint

The size of the spoon does not matter.

Solution

### Riddle #16: The Doodle Problem Is a Lot Harder Than It Looks. Can You Solve It?

(Difficulty: Moderate)

This week’s riddle is relatively simple—but sinister all the same.

The question: Can you make 100 by interspersing any number of pluses and minuses within the string of digits 9 8 7 6 5 4 3 2 1? You can’t change the order of the digits! So what’s the least number of pluses and minuses needed to make 100?

Andrew Daniels

For instance, 98 - 7 - 6 + 54 - 32 shows one way of interspersing pluses and minuses, but since it equals 107, it’s not a solution.

I call this a “doodle problem”: one that’s best worked on during meetings where you might be doodling otherwise.

#### Hint

You might want to start looking for solutions that use a total of seven pluses and minuses (although there are ways to use fewer).

### Riddle #17: This Math Puzzle Stumped Every Scientist but One. Think You Can Crack It?

(Difficulty: HARD)

In honor of Freeman Dyson, the renowned physicist who died last month, here’s a legendary tale demonstrating his quick wit and incredible brain power.

One day, in a gathering of top scientists, one of them wondered out loud whether there exists an integer that you could exactly double by moving its last digit to its front. For instance, 265 would satisfy this if 526 were its exact double—which it isn’t.

After apparently just five seconds, Dyson responded, “Of course there is, but the smallest such number has 18 digits.”

This left some of the smartest scientists in the world puzzling over how he could have figured this out so quickly.

So given Dyson’s hint, what is the smallest such number?

#### Hint

My second grader has recently learned how to add a 3-digit number to itself using the classic vertical method:

Andrew Daniels

18-digit numbers, of course, can be added in the same way.

Solution

### Riddle #18: Figure Out What’s on Her Forehead

(Difficulty: Moderate)

Cecilia loves testing the logic of her very logical friends Jaya, Julian, and Levi, so she announces:

“I’ll write a positive number on each of your foreheads. None of the numbers are the same, and two of the numbers add up to the third.”

She scribbles the numbers on their heads, then turns to Jaya and asks her what her number is. Jaya sees Julian has 20 on his forehead, and Levi has 30 on his. She thinks for a moment and then says, “I don’t know what my number is.” Julian pipes in, “I also don’t know my number,” and then Levi exclaims, “Me neither!” Cecilia gleefully says, “I’ve finally stumped you guys!”

“Not so fast!” Jaya says. “Now I know my number!”

What is Jaya’s number?

#### Hint

Jaya could be one of two numbers, but only one of those numbers would lead to Julian and Levi both not knowing their numbers. Why?

### Riddle #19: Can You Get Keanu Reeves Elected As President?

(Difficulty: Moderate)

It’s 2024, and there are five candidates running in the democratic primary: Taylor Swift, Oprah Winfrey, Mark Cuban, Keanu Reeves, and Dwayne Johnson. (Hey, it could happen.) As usual, the first primary is in Iowa.

In an effort to overcome its embarrassment after the 2020 caucus debacle, the Iowa Democratic Party has just announced a new, foolproof way of finding the best candidate: there will be four consecutive elections.

First, candidate 1 will run against candidate 2. Next, the winner of that will run against candidate 3, then that winner will run against candidate 4, and finally the winner of that election will run against the final candidate. By the transitive property, the winner of this last election must be the best candidate ... so says the Iowa Democratic Party.

Candidate Keanu has been feeling pretty low, as he knows he is ranked near the bottom by most voters, and at the top by none. In fact, he knows the Iowa population is divided into five equal groups, and that their preferences are as follows:

.

Keanu is childhood friends with Bill S. Preston, Esq., the new head of the Iowa Democratic Party. Preston, confident that the order of the candidates doesn’t matter for the outcome, tells Keanu he can choose the voting order of the candidates.

So what order should Keanu choose?

#### Hint

How would Keanu fare in one-to-one races against each candidate?

Solution

### Riddle #20: Who Opened All These Damn Lockers?

(Difficulty: Moderate)

There are 100 lockers that line the main hallway of Chelm High School. Every night, the school principal makes sure all the lockers are closed so that there will be an orderly start to the next day. One day, 100 mischievous students decide that they will play a prank.

The students all meet before school starts and line up. The first student then walks down the hallway, and opens every locker. The next student follows by closing every other locker (starting at the second locker). Student 3 then goes to every third locker (starting with the third) and opens it if it’s closed, and closes it if it’s open. Student 4 follows by opening every fourth locker if it’s closed and closing it if it’s open. This goes on and on until Student 100 finally goes to the hundredth locker. When the principal arrives later in the morning, which lockers does she find open?

#### Hint

Make sure you pay attention to all of the factors.

### 🎥 Now Watch This:

Laura FeivesonLaura Feiveson is an economist for the government, a storyteller, and a lifelong enthusiast of math puzzles.  She lives in Washington, DC with her husband and two daughters.

Sours: https://www.popularmechanics.com/science/math/a31153757/riddles-brain-teasers-logic-puzzles/

## Fun and Challenging Math Riddles & Games:

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### Math Riddles for Kids

Brain teasers and logic riddles play an important role especially in the mental development of high-school children. Let’s have a look at some of the best riddles with answers we’ve compiled for you and your kids:

How many circles contain the black dots?

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Dog=17 kg, cat and rabbit= 10 kg. The answer is 27 kg.

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### Circle and Square Equation

Can you solve the equation?

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Move just 2 matchsticks to make the equation correct!

9-9=0. Move one from the addition sign to make it a subtraction sign, and put it to 3 to make 9, 2. move one from 8 to make it 9.

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Can you find the missing number?

MentalUP offers fun educational brain teasers specially prepared by academics and child development experts for children of all ages:

Can you move four matchsticks to form three squares?

All of them are interesting, fun, and thought-provoking. Discover math riddles that are waiting for you on MentalUP now.

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### Math Riddles for Middle-School Children

Children need to solve different brain teaser puzzles and logic riddles based on their age and educational level. If you give a middle-school child extremely hard or impossible math riddles to solve, this may undermine his self-confidence. We have listed the math and logic riddles that are suitable for your child according to the grades:

Each ball has the value shown in the boxes below. Write the total of each horizon and vertical line of balls!

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There are 5 bags with 1,2,3,4,5 balls inside and two sizes of boxes. Put the bags into the boxes in a way that the big box has twice the number of balls than the smaller box. Find out all of the 3 ways to do so!

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Mark all 3 numbers that stand horizontally or vertically next to each other and make 10 when you add them.

How many triangles can you count in this shape?

There are triangles!

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How would you place the numbers 10, 20, 30, 40, 50, 60, 70 and 80 so that each side of the square adds up to 150?

How would you place the numbers 2, 4, 6, 8, 10, 12 and 16 so that the numbers in the hexagon are equal to the two numbers in the circles added together on either side.

There are 8 total possible solutions. 2 of the solutions are as below. The other 6 solutions are simply the rotated versions of those two.

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### Solve the Multiplication

How would you place the numbers from 1 to 6 to get the product?

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Each number in the hexagons is the sum of the two numbers below it. So what should be placed in the top hexagons?

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Here is a magic square in which each line of 3 numbers adds up to the same amount vertically, horizontally or diagonally. The total must be 7½. How will you place the numbers 0, ½, 1, 1½, 2, 2½, 3, 3½, 4, 4½?

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Start the maze with 0 and finish it with a total of 10. You can move to the right or down each turn. Find 3 different ways to do so!

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If the same proportion holds, what is the value of 1/3 of 10?

A merchant can place 8 large boxes or 10 small boxes into a carton for shipping. In one shipment, he sent a total of 96 boxes. If there are more large boxes than small boxes, how many cartons did he ship?

7 large boxes (7 x 8 = 56 boxes)

4 small boxes (4 x 10 = 40 boxes)

So the answer is 11 total cartons for 96 boxes

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Can you find the missing number?

The answer will be 2. Look at how many closed areas there are.

9999 has 4 closed areas (the top of the '9').

8888 has 8 closed areas (the top and bottom parts of 8 and there are no other digits).

1816 has 3 closed areas (top and bottom of 8 and bottom of 6, and it has 2 other digits (3 * 2 = 6)).

1212 has 0 closed areas, (0 * 4 = 0).

How can you add eight 8's to get the number 1,000? (only use addition).

The key to this math riddle is realizing that one place must be zero. 888 + 88 + 8 + 8 + 8 = 1,000

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A 35-year-old woman has 3 children. If you multiply the 3 children's ages, you get 36. If you add up the children's ages it's 13. And her oldest child plays basketball for 3 years.
How old are the kids?

They are 2, 2, and 9.

If you list out the trio of factors that multiply to 36, you get:

1 1 36 = 38

1 2 18 = 21

1 3 12 = 16

1 4 9 = 14

6 6 1 = 13

2 2 9 = 13

2 3 6 = 11

3 3 4 = 10

If the sum is 13, as you can see, there are 2 options. When she says her 'oldest' you know it cannot be {6, 6, 1} since she would have two 'older' sons, not an 'oldest'.

An athlete is jumping. However, every time she jumps she gets a bit more tired, and every jump goes 1/2 as far as her prior jump. Now, for her very first jump, she goes 1/2 of a foot. On her second jump, she goes 1/4 of a foot, and so on and so forth. How many jumps does it take for her to travel 1 foot?

She will never get to the 1-foot mark because you keep adding smaller and smaller amounts!

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Fun math riddles for adults is one of the best-known ways to keep your mind fresh. Since mathematics riddles make our brain muscles work, these are the exercises that adults generally prefer. Check out the best maths riddles for adults listed below:

Can you solve the equation?

A⁴= 2⁴-2, B⁴=3⁴-3 so following the same pattern C⁴=4⁴-4=252.

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Can you find the missing number?

The number that should replace the question mark is 9. Why? The sum of the three numbers on each die equals the number written below it. For the first die, for example: 8 + 4 + 7 = 19; for the second: 8 + 2 + 1 = 11. Following this pattern would explain why the third die is also 11 (5 + 5 + 1) and why the mysterious question mark should be 9 (4 + 3 + 2).

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Move the numbers from the outer frame onto the board so they snake together vertically, horizontally, or diagonally in sequence from 1 to 25. (For example, 2 must touch both 1 and 3.) The catch: You can only move a number in the direction indicated on its home square. Each number fits in its own cell.

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A whole number between one and seven belongs in each of the seven bubbles. Each number occurs once. The sums of some of the numbers are revealed in the areas where their bubbles overlap.
Can you figure out which number goes in each bubble?

Use the MentalUP app for more fun math riddles! Do daily brain exercises, track your progress and measure your performance in different cognitive skills.

Which glass will be filled first?

Because of the glasses, 5, 6 and 7 got a blocked connection. Now, since the connection to 3 is lower than that of 2, it will fill first while the remaining glasses will remain empty.

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How many squares are there in a chessboard?

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### Easy Math Riddle for Adults

An easy peasy math riddle for adults! How fast can you find the hidden pattern?

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How can we add 15 matchsticks in the picture below to create four areas of equal size? These kinds of math riddles for adults which will surely bring out the angry side of you!

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### Fun Math Riddle For Adults

Challenge yourself with fun math riddles for adults: How many triangles can you find in this picture?

It’s your turn. Don’t just watch, take action. Download MentalUP to test, train and improve your mind with over 100 tricky math riddles.

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This is one of the best fun math riddles for adults to keep them entertained: If you can move only 3 circles, can you turn it upside down?

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### Hard Math Riddles

Looking for incredibly challenging math riddles? Challenge is always good for our brains but there are really impossible math riddles that are just designed for geniuses! Here are some great examples of hard but not impossible ones for you:

Can you solve the equation?

Consider, number as: A + B + C

Now they are following this pattern: A + B + C = [AxB] [AxC] [(AxB)+(AxC)-(B)]

Where: [AxB] = First two digits

[AxC] = Further two digits [(AxB)+(AxC)-(B)] = Last two digits
E.g.: 5 + 3 + 2 =

First two digits: 5×3= 15

Further two digits: 5×2= 10

Last two Digits: 15 + 10 = 25 – 3(middle number from question) = 22

So, we get 5 + 3 + 2 = 151022

Same as: 7 + 2 + 5 = 143547

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You are running a race with three persons. You overtake the secondlast person, what position are you in NOW?

If your reply is the 2nd position, then you are just trapped in this puzzle trick just like many. The correct answer is the 3rd Position. You are running a race with three persons, that means the total number of people running in this race is four, and you passed the second-last person (i.e. The Third-person). Now you are in the third position.

Quick and fun math learning games that sharpen the players’ math and counting skills. Academic approach. Entertaining & Scientific games + no-ads.

Can you find the value of the missing number?

The outer number is the sum of the numbers in the two segments immediately across the line connecting big Circle to small Circle.

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The second digit is not important for the result.

Result =
first digit * first digit
third digit * third digit

398 = 964 (3*3 8*8)

118 = 164 (1*1 8*8)

356 = 936 (3*3 6*6)

423 = 169 (4*4 3*3)

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How can you make the following equation true by drawing only one straight line:

Draw a line on the first plus sign. This turns it into a 4! The equation then becomes correct: .

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### Find the Values of Numbers

All the math nerds! Here is a good challenge for you.

A = 6. B = 10. C = 18. D = 33

If you couldn’t find the answer don’t worry. MentalUP App has 100s of math riddles and games for you:

### Challenging Math Riddles

There are 12 checkers on a table, arranged as shown. Four adjacent checkers can be united in a square. Including the one outlined, how many possible groupings are there of four checkers that form a square?

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### Logical Hard Math Riddle

These kind of challenging math riddles aren't easy to solve. Do you think you know the answer to this one?

You might start doing some elaborate fractions but hard riddles like this are sometimes much more about word play than crunching the numbers.

Think literally and the answer may just appear right before your eyes. Answer: IV, the Roman numeral for four, which is “half” (two letters) of the word five.

MentalUP has interactive math puzzles and math games for all kids as well as for adults!

### Fun Math Riddles

When it comes to riddles, the sky's the limit! You can even find Christmas, Thanksgiving or Halloween math riddles with answers, as well as some really tricky and fun ones.

Below we have listed the most unusual and fun ones for you. Let’s see are you good enough to take on these mathematics riddles?

How do you make the number 7 an even number without addition, subtraction, multiplication, or division?

Drop the .

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It’s confusing but you can find the answer if you think differently.

Remove the 2 letters F and E from five and you have IV.

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### How Many Tickets Did They Buy in Total?

A grandmother, two mothers, and two daughters went to a baseball game together and bought one ticket each.
How many tickets did they buy in total?

(the grandmother is also a mother and the mother is also a daughter)

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If the tree grew by five centimeters each year, how much higher would the nail be?

The nail would be at the same height since trees grow at their tops.

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How many sides does a circle have?

. The inside and the outside.

Well done! Did you like it? Many of riddles and brain teasers waiting for you in MentalUP with Premium features!

What does one math book usually say to the other math book?

“Do you want to hear my problems?”

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### Challenging Math Riddles with Answer

My twin lives at the reverse of my house number. The difference between our house numbers ends in two. What are the lowest possible numbers for our house?

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### Egg Math Riddle with Answer

If you love math riddles with answers here’s a fan favorite for ages 10 and up, yet many people can't seem to get the correct answer.

I have , of course!

Play while you learn with math games and riddles full of fun! 🥰

21 July 2020Last Update Date: 23 February 2021
Lauran Cole

Sours: https://www.mentalup.co/blog/math-riddles
5 AMAZING AND FUN MATH RIDDLES FOR KIDS AND TEENS-SET A-INTERESTING MATH RIDDLES-TEST YOUR IQ LEVEL

## Brain Teasers Math Riddles Puzzles with Answers Easy Hard Tricky

Contents

In everyone life, Mental health is also important as physical health. For this, you need to exercise your brain. Therefore, Math Riddles or Math puzzles are the funniest way to exercise of brains. Nothing is better than solving a Math Riddles or Math puzzles.

To solve any math riddle, you need to use some fun strategies while approaching the solution of math riddles or math puzzles. Sometimes you need to pay some concentration, apply critical thinking, and logical reasoning to solve these math riddles or math puzzles.

Now, there are following math riddles with answers.

### Easy Math Riddles with Answers

Easy Math Riddle 1 with Answer : Using only addition, how can you add eight 8s to get the number 1,000?

Easy Math Riddle 2 with Answer : A man is twice as old as his little sister. He is also half as old as their dad. Over a period of 50 years, the age of the sister will become half of their dad’s age. What is the age of the man now?

### Hard Math Riddles with Answers

Hard Math Riddle 1 with Answer : A grandfather, two fathers and two sons went to the movie theater together and everyone bought one movie ticket each. How many tickets did they buy in total?

Hard Math Riddle 2 with Answer : If it took 8 people 10 hours to build a barn, how long would it take 14 people to build the same barn?

### Tricky Math Riddles with Answers

Tricky Math Riddle 1 with Answer : Jack lives at the reverse of Mack’s house number. The difference between our house numbers ends in two. What are the lowest possible numbers of our house?

Tricky Math Riddle 2 with Answer : In ‘the alphabet, there are x letter, where x is not 26.’ Find x.

### Math Riddles with Pictures

Math Riddle 1 with Pictures : The number 4 is half of 5 How?

Math Riddle 2 with Pictures : I have three letters. Remove first letter, I become stronger. Remove first two letters, I become 10. What I am?

### Math Riddles for Kids with Answers

Math Riddle 1 for Kids with Answer : I am an odd number. Take an alphabet away from me and I become even. Who I am?

Math Riddle 2 for Kids with Answer : If it took 15 people 20 hours to build a wall, how long would it take 24 people to build the same barn

### Math Riddles for Kindergarten with Answers

Math Riddle 1 for Kindergarten with Answer : I am a number between zero and ten. I am more than two. I am before four. Who I am?

Math Riddle 2 for Kindergarten with Answer : What can you put between a 7 and an 8 so that the result is greater than 7, but less than 8?

Math Riddle 1 for First Graders with Answer : Why do plants hate math?

Math Riddle 2 for First Graders with Answer : What did one math book say to other?

Math Riddle 1 for Second Graders with Answer : If a hen and a half lay an egg and a half in a day and a half, how many eggs will half a dozen hens lay in half a dozen days?

Math Riddle 2 for Second Graders with Answer : You have two coins. Added together, they equal 15 cents, but one it not nickel. How is that possible?

Math Riddle 1 for Third Graders with Answer : What is the next number in the sequence below? 1, 4, 9, 16, 25, 36, …

Math Riddle 2 for Third Graders with Answer : You have two coins. Added together, they equal 15 cents, but one it not nickel. How is that possible?

Math Riddle 1 for Fourth Graders with Answer : How many volumes of dirt are in a PVC pipe of 50-meter-long and 30 meter wide?

Math Riddle 2 for Fourth Graders with Answer : How can you write eleven thousand eleven hundred and eleven in numbers?

Math Riddle 1 for Fifth Graders with Answer : What is occur once in every minute, twice in every moment, and never in a thousand years?

Math Riddle 2 for Fifth Graders with Answer : Divide 250 into two so that one will be 400 percent of the other. What are the numbers?

Math Riddle 1 for Sixth Graders with Answer : What will be the sign of the product if you multiply together 201 negative numbers and 20 positive numbers?

Math Riddle 2 for Sixth Graders with Answer : A rope of length 39/4 m is cut into 6 pieces of equal length. Find the length of the each piece.

Math Riddle 1 for Seventh Graders with Answer : If A : B = 2 : 3 and B : C = 5 : 7, then find the ratio A : B : C.

Math Riddle 2 for Seventh Graders with Answer : A number is decreased by 40% gives 180. Find the number.

Math Riddle 1 for Eighth Graders with Answer : What is the next number in the sequence below? 1, 4, 9, 16, 25, 36, …

Math Riddle 2 for Eighth Graders with Answer : You have two coins. Added together, they equal 15 cents, but one it not nickel. How is that possible?

Math Riddle 1 for Ninth Graders with Answer : A’s income is 60% more than of B’s. By what percent is B’s income less than A’s?

Math Riddle 2 for Ninth Graders with Answer : If 1A2B5 is exactly divisible by 9, then find the least value of (A + B).

Math Riddle 1 for Tenth Graders with Answer : Five people were eating chocolates, A finished before B, but behind C. D finished before E, but behind B. What was the finishing order?

Math Riddle 2 for Tenth Graders with Answer : A man has 53 socks in his drawer: 21 identical blue, 15 identical black and 17 identical red. The lights are out and he is completely in the dark. How many socks must he take out to make 100 percent certain he has at least one pair of black socks?

### Math Riddles for Teens with Answers

Math Riddle 1 for Teens with Answer : If 2 + 2 = 44, 3 + 3 = 96, 4 + 4 = 168, 5 + 5 = 2510, then what is the value of 6 + 6?

Math Riddle 2 for Teens with Answer : If 5 + 5 = 52, 6 + 6 = 63, 7 + 7 = 94, 8 + 8 = 46, then find the value of 9 + 9.

### Math Riddles for Middle High School Students with Answers

Math Riddle 1 for Middles High School Students with Answer : If there are 70 students in your class and you shake every student’s hand when you arrive, how many handshakes will you have to make?

Math Riddle 2 for Middles High School Students with Answer : You have 10 rose bushes and need to plant them in 5 rows. Each row has to have 4 bushes. How would you do this?

### Math Riddles for High School Students with Answers

Math Riddle 1 for High School Students with Answer : With the numbers 123456789, make them add up to 100. They must stay in the same order. You can use addition, subtraction, multiplication, and division. Remember, they have to stay in the same order.

Math Riddle 2 for High School Students with Answer : If 1 + 9 + 8 = 1, then find the value of 2 + 8 + 9.

Math Riddle 1 for Adult with Answer : What’s the angle between the minute hand and hour hand at a quarter past three?

Math Riddle 2 for Adult with Answer : If you count 20 houses on your right going to school and 20 houses on your left coming home, how many houses did you count?

## Math Riddles

Other Math Brain Teasers:
##### Riddle 1

How can you add eight 8's to get the number 1,000? (only use addition).

The key to this math riddle is realizing that the one place must be zero. 888 + 88 + 8 + 8 + 8 = 1,000.

##### Riddle 2
Two Fathers and Two Sons Riddle

Two fathers and two sons sat down to eat eggs for breakfast. They ate exactly three eggs, each person had an egg. The riddle is for you to explain how.

One of the 'fathers' is also a grandfather. Therefore the other father is both a son and a father to the grandson.

In other words, the one father is both a son and a father.

##### Riddle 3
Digit Frequency

Part I. What digit is the most frequent between the numbers 1 and 1,000 (inclusive)? To solve this riddle you don't want to manually do all of the math but rather try to figure out a pattern.

The most common digit is '1.' Can you figure out why? No hints until you try the next riddle because the next riddle is closely tied to this one.

Part II. What digit is the least frequent between the numbers 1 and 1,000?

0 is the least common digit even though 1,000 has three zero's!

Explanations for both riddles
The digits 0 through 9 all follow the same pattern there is exactly 1 occurrence of each digit for every ten numbers.

• For instance the digit 2 appears once between 10 and 19, at 12. And 2 appears once between, 30 and 39 at 32.
• However, each of the digits 1 through 9 also appear in other numbers in the tens and hundreds place.

Again, let's look at 2 which appears in 20, 21, 22, 23, etc.. as well as 200, 201, 202, 203.

So to figure out how to answer the first riddle you had to see what distinguishes the number 1? Only that we are including 1,000 which would be the first '1' in a new series of ten! In other words, the digit 1 only has a single extra occurrence (301 occurrences) compared to 2 or 3 or 9 which each have exactly 300 occurrences.

The reason that zero has the least (BY FAR at only 192 occurrences) is because zero does not have any equivalents to 22, 33, 44, 222, 3333 etc.

##### Riddle 4
Three Guys at A Hotel Riddle

Three guys rent a hotel room for the night. When they get to the hotel they pay the $$\30$$ fee, then go up to their room. Soon the bellhop brings up their bags and gives the lawyers back $$\5$$ because the hotel was having a special discount that weekend. So the three lawyers decide to each keep one of the $$\5$$ dollars and to give the bellhop a $$\2$$ tip. However, when they sat down to tally up their expenses for the weekend they could not explain the following details:

Each one of them had originally paid $$\10$$ (towards the initial $$\30$$), then each got back $$\1$$ which meant that they each paid $$\9$$. Then they gave the bellhop a $$\2$$ tip. HOWEVER, 3 • $$\9$$ + $$\2$$ = $$\29$$.

The guys couldn't figure out what happened to the other dollar. After all, the three paid out $$\30$$ but could only account for $$\29$$.

Can you determine what happened?

There are many ways of explaining/thinking about this truly brain bending riddle! It all boils down to the fact that the lawyers's math is incorrect.

They did NOT spend $$\9$$ • 3 + $$\2$$.

They spent exactly $$\27$$ dollars. $$\25$$ for the room and $$\2$$ for the tip. Remember they got exactly $$\3$$, in total back.

Another way to think about the answer to this riddle is to just pretend that the bellhop refunded $$\3$$ to the lawyers (rather than giving them $$\5$$ and receiving $$\2$$ back).

If the lawyers get $$\3$$ back and each takes $$\1$$. Then they spent exactly $$\27$$ dollars.

##### Riddle 5
Foreign Country Riddle

In a certain country ½ of 5 = 3. If the same proportion holds, what is the value of 1/3 of 10?

##### Riddle 6
The Merchant

A merchant can place 8 large boxes or 10 small boxes into a carton for shipping. In one shipment, he sent a total of 96 boxes. If there are more large boxes than small boxes, how many cartons did he ship?

11 cartons total
7 large boxes (7 * 8 = 56 boxes)
4 small boxes (4 10 = 40 boxes
11 total cartons and 96 boxes

##### Riddle 7
Crossing the River

A farmer is trying to cross a river. He is taking with him a rabbit, carrots and a fox, and he has a small raft. He can only bring 1 item a time across the river because his raft can only fit either the rabbit, the carrots or the fox. How does he cross the river. (You can assume that the fox does not eat the rabbit if the man is present, you can also assume that the fox and the rabbit are not trying to escape and run away).

The key to solving this riddle is realizing that you have to take the rabbit over first and the switch the fox with the rabbit. See step 2.

Step 1

Take the rabbit to the other side.

 Shore Other Side CarrotsFox Rabbit
Step 2

Go back and get the Fox and switch it with the Rabbit.
**The key here is that the carrots and the rabbit are not being left alone.

 Shore Other Side Carrots Rabbit(Not left alone) Fox
Step 3
 Shore Other Side Rabbit FoxCarrots
Step 4

Go back and get the rabbit.

 Shore Other Side RabbitFoxCarrots
##### Riddle 8
Three Brothers on a Farm

Three brothers live in a farm. They agreed to buy new seeds: Adam and Ben would go and Charlie stayed to protect fields. Ben bought 75 sacks of wheat in the market whereas Adam bought 45 sacks. At home, they split the sacks equally. Charlie had paid 1400 dollars for the wheat. How much dollars did Ben and Adam get of the sum, considering equal split of the sacks?

Every farmer's part is $$1/3(45+75) = 40$$ sacks.
Charlie paid $$\1400$$ for $$40$$ sacks, then 1 sack costs $$\1400/40 = 35/{\text{sack}}$$.

Adam got $$\35*(45-40)=35*5 = \175$$.
Ben got $$\35*(75-40)=35*35 = \1225$$.
Answer: Ben $$\1225$$, Adam $$\175$$

##### Riddle 9
The Insurance Salesman

An insurance salesman walk up to house and knocks on the door. A woman answers, and he asks her how many children she has and how old they are. She says I will give you a hint. If you multiply the 3 children's ages, you get 36. He says this is not enough information. So she gives a him 2nd hint. If you add up the children's ages, the sum is the number on the house next door. He goes next door and looks at the house number and says this is still not enough information. So she says she'll give him one last hint which is that her oldest of the 3 plays piano.

Why would he need to go back to get the last hint after seeing the number on the house next door?

Because the sum of their ages (the number on the house) is ambiguous and could refer to more than 1 trio of factors.

{2, 2, 9}

If you list out the trio of factors that multiply to 36 and their sums, you get:

• 1 1 36 = 38
• 1 2 18 = 21
• 1 3 12 = 16
• 1 4 9 = 14
• 6 6 1 = 13
• 2 2 9 = 13
• 2 3 6 = 11
• 3 3 4 = 10

Since the number on the house next door is not enough information there must be more than 1 factor trio that sums up to it, leaving two possibilities: { 6, 6, 1} , {2, 2, 9} . When she says her 'oldest' you know it can not be {6, 6, 1} since she would have two 'older' sons not an 'oldest'.

##### Riddle 10
The Monty Hall

This is a famous one. The classic Monty hall riddle!

You are confronted by 3 doors. Behind one of them is a car, behind the two others, you will only see a goat. Now, if you correctly pick the car, you win the car! Otherwise, if you get one of the 2 goats, you don't get the car.

So, pick any door. It doesn't matter which one, but we will suppose that you picked door #2, as an example.

Should You switch?

Now, after you have picked a door and before finding out what is actually behind it, you are shown a goat behind one of the other doors. (Remember there has to be a goat in 1 of the doors that you have not picked.)

Let's say you choose door #2, as shown above. For example's sake, let's say there's a goat in door 1. The question and the riddle is: should you switch the door that you picked? In other words, in this example, should you now choose door 3? Or, should you stick with your first choice (door #2)?

There actually is a mathematically correct answer to this riddle: You should indeed change your choice. If you don't believe me, just try out our free online Monty hall simulation.

##### Riddle 11

If 9999 = 4, 8888 = 8, 1816 = 6, 1212 = 0, then 1919 =

4

Look at how many closed areas there are.

• 9999 has 4 closed areas (the top of the '9').
• 8888 has 8 closed areas, the top and bottom parts of the 8 and there are no other digits.
• 1816 has 3 closed areas, (top and bottom of 8 and bottom of 6, and it has 2 other digits (3 * 2 = 6)).
• 1212 has 0 closed areas, (0 * 4 = 0).
##### Riddle 12

An athlete is able to jump FOREVER. However, everytime that she jumps she gets a bit more tired, and every jump goes $$\frac 1 2$$ as far as her prior jump. Now, for her very first jump, she goes $$\frac 1 2$$ of a foot.

On her second jump, she goes $$\frac 1 4$$ of a foot, and so on and so forth. The beginning of her journey is shown in the gif below.

How many jumps does it take for her to travel 1 foot?

She will never get to the 1 foot mark because you keep adding smaller and smaller amounts!

Zeno's paradox of Achilles and the Tortoise

Quick summary of riddle: Zeno of Elea (490-425 BC) is known for creating many paradoxes which were debated by mathematicians for centuries. His riddle involving Achilles, the character from Homer's Iliad and a tortoise went something like:

The tortoise challenged Achilles to a race and Achilles, full of typical hubris, accepted and even gave the Tortoise a 10 foot head start. Before the race started, the tortoise told Achilles that the reason Achilles would lose is that even though Achilles would be catching up, the tortoise would always be moving ahead. Therefore, Achilles would always be covering a fraction of the distance between the two. Let's say he covered half of the distance in 1 second (5 feet) and then in the next he covered half of the new distance, the remaining 5 feet plus the Tortoise's new distance. In the end, the tortoise convinced Achilles that he could not win the race because although he would be getting closer and closer, he would still always be covering smaller and smaller fractions of the total distance between the two. Therefore, Achilles forfeited the race. To read this riddle in a modern narrative form click here.

Other Math Brain Teasers:
Sours: https://www.mathwarehouse.com/riddles/math-riddles.php

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