Math riddles are tricky problems or questions that students have to use their knowledge of math operations, vocabulary, and general knowledge to solve. They’re also a fun way to engage in creative thinking and collaboration as they work to solve math riddles together.
As a warm-up or challenge activity, math riddles:
- Improve problem-solving skills.
- Build resilience. Students are bound to miss one (or many) riddles. Having to try and try again is a skill they’ll need in math and beyond.
- Increase engagement. Math riddles can be a fun way to learn and practice math, which can increase motivation.
- Support collaboration. If students must solve a problem in groups, they’ll practice working together and relying on each other’s unique approaches and thinking styles.
Whatever the reason, check out these 100 math riddles to challenge every student.
Math Riddles for Elementary School
How many sides does a circle have?
None. A circle does not have sides.
I’m an even, single-digit number. Once you write me, I have no start or end. I look like a standing pair of glasses. Who am I?
8.
Ashley buys one new toy every 30 days. How many toys does he have in one year?
12.
Which is longer, 10 centimeters or 10 inches?
10 inches.
If you multiply me by any other number, the answer will always be the same. What number am I?
Zero.
What weighs more, a pound of feathers or a pound of bricks?
They weigh the same.
When Pam was 8, her sister was half her age. Now, Pam is 14. How old is her sister?
Pam’s sister is 4 years younger, so her sister is now 10 (14 – 4 = 10).
If a boy blows 18 bubbles, and then he pops 7, eats 6, stomps 5, and blows another 1, how many are left?
One.
If you’re at a theater to watch a movie that starts in one hour, how many minutes do you have to wait to watch it?
60 minutes.
Nina has six siblings who were born two years apart. Kevin, the youngest, is 7 years old, while Nina is the oldest. How old is Nina?
Nina is 19: 7 + 2 + 2 + 2 + 2 + 2 + 2 = 19.
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.
What is the Roman numeral for 100?
C.
You’re 8 years old, and your uncle is 53. How old will your uncle be when you are 23?
68.
At what point do parallel lines meet?
Never. Parallel lines never intersect.
If it took seven people 10 hours to build a doghouse, how many hours will it take 15 people to build the same doghouse?
None. The dog house is already built.
A farmer has 23 goats on his farm. One day after a storm, all but 9 ran away. How many goats does the farmer have now?
Nine.
Place three matches on the table. How can you add two more to make eight?
Add two matches to make the Roman numeral VIII.
How many times can you take 10 away from 100?
Once. After that, the number you’re subtracting from is 90.
There’s something common between the numbers 11, 88, and 96. What is it?
You can rotate them 180° or upside down and they will still look the same.
What can you put between 8 and 9 to make the result greater than 8, but less than 9?
A decimal point (8.9).
This number is the smallest prime number and an even number. What is it?
Two.
Henry is 1,000 mm tall, and Hank is 100 cm tall. Who’s taller?
They are the same height.
Can you find a way to get the number 23 by using only the number 2?
22 + 2/2 = 23
How many cupcakes are in a baker’s dozen?
Thirteen.
I get 11 when I add 5 and 6, but when I take 7 and 6, I get 1. What am I?
A clock.
If 1 = 4, 2 = 8, 3 = 12, then 4 = how much?
Since 1 = 4, then 4 = 1.
There is an odd number that becomes even if you take away one letter from it. What is it?
Seven. Take away the S and it is “even.”
What three numbers have the same result if they are added or multiplied together?
1, 2, and 3.
If days on Mars are as long as two weeks on Earth, how long is an hour?
14 Earth hours.
Math Riddles for Middle Schoolers
If you go to the movies and you’re paying, is it cheaper to take one friend to the movies twice or two friends to the movies at the same time?
It is cheaper to take two friends at the same time, since you’d be paying for yourself plus two others (three people) as opposed to paying for yourself and one friend twice, which equals four people.
If four men can build four tables in four hours, how many can eight men build in eight hours?
16.
I am four times as old as my daughter. In 20 years time, I shall be twice as old as her. How old are we now?
I am 40 and my daughter is 10.
There is a lily pad on a small pond. Each day, the lily pad doubles its size. On day 20 it covers the whole pond. On what day was the lily pad the size of half the pond?
Day 19.
At a clothing store, the owner has devised his own method of pricing items. A vest costs $20, socks cost $25, a tie costs $15, and a blouse costs $30. Using this method, how much would a pair of underwear cost?
$45. The pricing method consists of charging $5 for each letter required to spell the item.
One is to three as three is to five and five is to four and four is the magic number. What is the pattern?
The word “one” has three letters. The word “three” has five letters. “Five” has four letters. “Four” has four letters.
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 three possible solutions.)
51 and 15, 42 and 24, or 60 and 06.
Pick a number from 1 to 10, multiply it by 2, add 10, divide it by 2, now subtract the number you picked from your total. What is it?
Five.
You want to boil a two-minute egg. If you only have a three-minute timer (hourglass), a four-minute timer, and a five-minute timer, how can you boil the egg for only two minutes?
Once the water is boiling, turn the three-minute timer and five-minute timer over. When the three-minute timer runs out, put the egg in the boiling water. When the five-minute timer runs out, two minutes have elapsed and it is time to take the egg out of the water. You do not need the four-minute timer.
81 x 9 = 801. What must you do to make the this equation true?
Turn it upside down. 108 = 6 x 18.
How much will a 38° angle measure when looked at under a microscope that magnifies 10 times?
It will be 38 degrees.
If 1 = 5, 2 = 15, 3 = 215, and 4 = 3,215, what does 5 equal?
5 = 1, because 1 = 5.
If seven people meet one another and each shakes hands only once with each of the others, how many handshakes happened?
21.
Using only addition, how can you add eight 8s to get the number 1,000?
888 + 88 + 8 + 8 + 8 =1,000.
How much dirt is there in a hole that is 3.45 m by 6.21 m?
None. There is no dirt in a hole.
A phone and case cost $110 in total. The price of the phone is $100 more than the case. How much is the phone?
$105.
An empty bus pulls up to a stop, and 10 people get on. At the next stop, 5 people get off, and twice as many people get on as at the first stop. At the third stop, 25 get off. How many people are on the bus?
One—the driver.
During what month do people sleep the least?
February because it has the fewest days.
There are 12 kids in a class. Six kids are wearing socks, four are wearing shoes, and three are wearing both. How many have bare feet?
Five.
Mr. Kim has five sons. Each of his sons has a sister. How many children does Mr. Kim have?
Six. They all have the same sister.
There are six chocolates in a basket. Six people each take one chocolate. How can it be that one chocolate is left in the basket?
The last person took the basket with the chocolate in it.
Kevin finished half of his report at school. He finishes another quarter after school. How much does he have left to finish?
A quarter (1 – 1/2 – 1/4 = 1/4).
What is the next number? 1, 2, 4, 7, 11, 16, __?
22.
At an ice cream shop, a single scoop costs $5. A double scoop costs $7. A triple scoop costs $8. What’s the best value?
The triple scoop.
Maria made brownies. She cuts the brownies into 12 equal pieces. How many cuts did she make?
Five cuts (two vertical, three horizontal).
Hailey has three library books at home. She finished reading one of them and returned it. Then her mom bought her two books. How many books does she currently have at home?
Four (3 – 1 + 2 = 4).
Which statement is correct: “Eight and six are fifteen” or “six and eight are fifteen”?
Neither of them is correct: 8 + 6 =14.
Math Riddles for High Schoolers
Cara leaves New York at 8 a.m., driving 35 mph. Nancy starts driving to New York at 50 mph. When they meet, which one will be farthest away from New York?
They will be the same distance from New York.
A teacher says that there are fewer than 30 students but more than 20 in a classroom. The children can be divided into groups of two, three, four, six, and eight with no leftover students. How many students are in the class?
24.
Seven brothers were born two years apart. The youngest brother is 7. How old is the oldest brother?
19.
Charlie has one child, a boy. He’s having another child. What chance does he have of having another boy?
50%.
What is the next number: 1, 3, 7, 15, 31, __?
63.
What is the next number: 2, 4, 6, 10, 16, __?
26.
There are 100 houses in the neighborhood where Sam and his brother live. Sam’s house number is the reverse of his brother’s house number. The difference between their house numbers ends with 2. What are their house numbers?
19 and 91.
In a three-digit number, the second digit is four times greater than the third digit. The first digit is three lower than the second digit. What is the number?
141.
It is raining at midnight and the weather forecast says that tomorrow and the next day will be clear. Will it be sunny in 48 hours?
No, in 48 hours, it will be night so it will not be sunny.
A 300-foot train traveling 300 feet per minute must travel through a 300-foot-long tunnel. How long will it take the train to travel through the tunnel?
Two minutes. It takes the front of the train one minute, and the rest of the train will take two minutes to clear the tunnel.
Robert and David played several golf matches against each other in a week. They played for a pizza at each match, but no pizzas were purchased until the end of the week. If Robert and David had the same number of wins at any time, those pizzas were canceled. Robert won four matches (but no pizzas), and David won three pizzas. How many rounds of golf were played?
11. David won seven matches—four to cancel out Robert’s four wins and three more to win the pizzas.
I add 5 to 9 and get 2. The answer is correct, but how?
When it is 9 a.m., add five hours to it, and you will get to 2 p.m.
When Carlos was 6 years old, his little sister, Julia, was half his age. If Carlos is 40 years old today, how old is Julia?
37.
Tom was asked to paint numbers outside 100 apartments, which means he will have to paint numbers 1 through 100. How many times will he have to paint the number 8?
20.
There are 100 pairs of dogs in a zoo. A pair of puppies are born for each dog. Unfortunately, 23 of the dogs have not survived. How many dogs are left in total?
977 dogs. 100 x 2 = 200; 200 + 800 = 1,000; 1,000 – 23 = 977
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?
Two dozen.
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 one tank too many. How many turtles and how many tanks does Leon have?
He has three tanks and four turtles.
Math Riddles for Adults
You have a perfect cube. Can you divide your cube into smaller cubes that all have different volumes?
No. There is no way for cubes of all different volumes to correctly fit inside of a larger cube. There would be empty spaces as the cubes got smaller and smaller and you would have no way to fill these spaces. Eventually, the cubes would be too small to continue.
One morning you need to find some socks, but your light is broken. You know there are 10 purple socks and 10 orange socks in your drawer, but they’re all mixed up. They are completely the same except for their color. How many socks do you have to pick to ensure you have a matching pair?
You only have to pick three socks. Because there are only two colors of socks in the drawer, you will definitely have a matching pair if you take three.
You are cutting up a pie. First you cut it into two pieces. With your next cut, you produce four pieces. The third cut results in seven pieces. How many pieces can you cut with seven slices?
29.
What is special about the number 854,917,632?
It’s the numbers one through ten in alphabetical order.
You are 8 feet away from a door, and with each move you advance half the distance to the door. How many moves will it take to reach the door?
You will never reach it because you will always have another half distance to cross.
Joe has 10 coins totaling $1.19. From these coins, he cannot make exact change for a dollar, half dollar, quarter, dime, or nickel. What are the coins?
A half dollar, a quarter, four dimes, and four pennies.
When shipping something, Tom can place 10 small boxes or 8 large boxes into a carton. A total of 96 boxes were sent in one shipment and the number of small boxes was less than large boxes. How many cartons did he ship?
11 cartons.
A certain number has three digits. The sum of the three digits equals 36 times this number. Seven times the left digit plus nine equals five times the sum of the two other digits. Eight times the second digit minus nine 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
Easy Math Riddles
I am a number that is 5 more than the number of toes you have on your feet. What am I?
15.
I am a number that is two more than the number of days in a week. What am I?
9.
I’m less than 15 but more than 10. You can find me by adding 10 to 3. What am I?
13.
I am more than 10 but less than 14. I am one more than the number of months in one year. What am I?
13.
I’m less than 8 but more than 5. I’m one more than the fingers on your left hand. What am I?
6.
I’m a number you can find by adding the number of sides of a triangle. What am I?
3.
I’m between 1 and 5. I’m less than 4 and more than 2. What am I?
3.
I am a number you get when you add the sides of a rectangle and a square.
8.
Hard Math Riddles
A snail is at the bottom of a 20-meter pit. Every day the snail climbs 5 meters up, but at night it slides down 4 meters. How many days does it take before the snail reaches the top?
The snail reaches the top of the pit on the 16th day. On the first day, the snail reaches a height of 5 meters and slides down 4 meters at night, and thus ends at a height of 1 meter. 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. On the 15th day, he reaches 19 meters but slides back to 15 meters. On the 16th day, he reaches 20 meters, so now he is at the top of the pit.
There are eight balls with eight different numbers in them: 1, 3, 5, 7, 9, 11, 13, 15. Select three balls that equal 30.
Flip the nine and turn it into a 6 and then the three balls are 6, 11, and 13.
Can you make 24 from the numbers 3, 3, 8, and 8? You can only use the operations + – x / (), and you have to use all four numbers.
8 / (3 – 8/3) = 24.
How can you take 2 from 5 and leave 4?
Remove the 2 letters F and E from five and you have IV which is the Roman numeral for four.
Granny left half her money to her granddaughter and half that amount to her grandson. She left a sixth to her brother, and the remainder, $1,000, to the dogs’ home. How much did she leave altogether?
Focus on the fractions. Add one-half, one-quarter, and one-sixth for a total that is a fraction of twelfths (2 + 4 + 6 = 12). You can also think about it as 6/12, 3/12, 2/12, which equals 11/12. If the remainder is $1,000, that must be one-twelfth, so the total is $12,000.
What single digit appears most frequently between and including the numbers 1 and 1,000?
The most common digit is 1. Every number 1 through 9 appears exactly the same number of times in every 10 numbers. But because we included the number 1,000, there’s an extra occurrence of the number 1. In total, the number 1 appears 301 times, and every other number appears 300 times.
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?
47.
What is the smallest whole number that is equal to seven times the sum of its digits?
21.
What is the smallest number that increases by 12 when it is flipped and turned upside-down?
86.
You have two U.S. coins worth a total value of 30 cents. One of them is not a nickel. What are the two coins?
One quarter and one nickel.