Sixty math riddles for kids aged 6 to 12, with answers. They start with counting and adding for younger kids, go on to taking away, times and sharing, money and time, shapes and patterns, and end with trick riddles where the numbers are not the point.
In this deck · 6 groups
Counting and adding
Add me to myself and you get 10. What number am I?
Then ask: What number would you double to get 20?
Answer: 5.
Why it works: 5 + 5 = 10. Adding a number to itself doubles it, so you need half of 10.
Three birds sit on a fence. Two more land, then one more. How many birds are on the fence?
Then ask: What if one flew away at the end?
Answer: 6.
Why it works: 3 + 2 = 5, then 5 + 1 = 6.
How many legs do a cat, a chicken and a fish have all together?
Then ask: Which animal did you almost forget, and why?
Answer: 6.
Why it works: A cat has 4 legs, a chicken has 2 and a fish has none, so 4 + 2 + 0 = 6.
I come right after the biggest one-digit number. What number am I?
Then ask: What comes right after the biggest two-digit number?
Answer: 10.
Why it works: The biggest one-digit number is 9, and the number after it is 10, the first number with two digits.
Sam has 4 red blocks and 3 blue ones. His sister gives him as many green blocks as he has blue ones. How many blocks does he have now?
Then ask: Which number in the story did you use twice?
Answer: 10.
Why it works: 4 + 3 = 7 blocks, and 3 green ones make 7 + 3 = 10.
What do you get if you add up all the dots on a die?
Then ask: Is there a quick way? Try pairing 1 with 6.
Answer: 21.
Why it works: 1 + 2 + 3 + 4 + 5 + 6 = 21. The quick way: 1 + 6, 2 + 5 and 3 + 4 each make 7, and 7 + 7 + 7 = 21.
Add 1 to me and I become a dozen. What number am I?
Then ask: What else comes in dozens?
Answer: 11.
Why it works: A dozen means 12, and 11 + 1 = 12.
Three kids walk into a room barefoot. How many toes walked in?
Then ask: How many if one kid puts socks on? Do the toes disappear?
Answer: 30.
Why it works: Each kid has 10 toes, so 10 + 10 + 10 = 30.
Add up the wheels on a bike, a car and a tricycle. What do you get?
Then ask: Can you name something with just one wheel?
Answer: 9.
Why it works: A bike has 2 wheels, a car has 4 and a tricycle has 3, so 2 + 4 + 3 = 9.
I am a two-digit number. My digits add up to 3, and my tens digit is the bigger one. What am I?
Then ask: Two answers work. What clue would leave just one?
Answer: 21 or 30.
Why it works: The digits must add to 3, so they are 1 and 2 or 3 and 0. Put the bigger digit in the tens place and you get 21 or 30.
Every answer shows how to work it out, step by step. Read the riddle, let your kid try, and ask how they got their answer before you say whether it's right. A wrong answer with a reason tells you more than a lucky right one.
Keep a pencil and paper nearby for the longer ones. For riddles without numbers, see the main list of 150 riddles.
Rather not read them out yourself? Thonko asks your kid math riddles out loud and wants to hear how they got each answer.
Taking away
You have 10 cookies and eat all but 3. How many are left?
Then ask: Did you start to subtract? What stopped you?
Answer: 3.
Why it works: "All but 3" means you ate every cookie except 3, so 3 are left.
There are 5 apples on the table, and you take 2. How many apples do you have?
Then ask: How would you change the question so the answer is 3?
Answer: 2.
Why it works: The 2 you took are the ones you have. The other 3 are still on the table.
I am 4 less than 10 and 2 more than 4. What number am I?
Then ask: Can you make a clue like that for 8?
Answer: 6.
Why it works: 10 − 4 = 6 and 4 + 2 = 6, so both clues point to 6.
Ana is 7, and her brother is 3 years older. How old will her brother be when Ana is 10?
Then ask: Was there ever a time when he was twice her age?
Answer: 13.
Why it works: Her brother is always 3 years older, so when Ana is 10 he is 10 + 3 = 13.
A bus has 9 people on it. At the first stop 4 get off and 2 get on. How many people are on the bus?
Then ask: Did you count the driver? Should you?
Answer: 7.
Why it works: 9 − 4 = 5, then 5 + 2 = 7. With the driver it would be 8.
Take 5 away from me and you get 5. What number am I?
Then ask: What number gives you 3 when you take 7 away?
Answer: 10.
Why it works: To undo taking 5 away, add the 5 back: 5 + 5 = 10.
You are 8th in line. How many people are in front of you?
Then ask: If 3 people stand behind you, how many are in the line?
Answer: 7.
Why it works: Being 8th means 7 people come before you.
A candle is 10 inches tall and burns down 2 inches every hour. How tall is it after 3 hours?
Then ask: When will it be gone?
Answer: 4 inches.
Why it works: In 3 hours it burns 2 + 2 + 2 = 6 inches, and 10 − 6 = 4.
Tom has 5 more marbles than Lily. Together they have 15. How many does Tom have?
Then ask: How could you check your answer?
Answer: 10.
Why it works: Set Tom's extra 5 aside and 10 are left to split evenly, 5 each. Tom gets his 5 plus the extra 5, so 10, and Lily has 5.
There are 3 steps up to the porch. You go up and back down twice. How many steps did you take?
Then ask: Did you count both trips?
Answer: 12.
Why it works: Up and down once is 3 + 3 = 6 steps, and doing it twice is 6 + 6 = 12.
Times and sharing
A spider has 8 legs. How many legs do three spiders have?
Then ask: How many spiders would it take to have 40 legs?
Answer: 24.
Why it works: 8 + 8 + 8 = 24, which is the same as 3 × 8.
Four kids share 12 grapes so everyone gets the same. How many does each kid get?
Then ask: What if a fifth kid shows up? Can they still share evenly?
Answer: 3.
Why it works: 12 split into 4 equal piles is 12 ÷ 4 = 3.
How many fingers are there on five hands?
Then ask: And on five people?
Answer: 25.
Why it works: Each hand has 5 fingers, and 5 × 5 = 25.
A pizza is cut into 8 slices. You and three friends share it evenly. How many slices does each person get?
Then ask: Who did you forget to count at first?
Answer: 2.
Why it works: You plus three friends makes 4 people, and 8 ÷ 4 = 2.
Juice boxes come 6 to a pack. How many packs do you need for 20 kids?
Then ask: What would you do with the extra boxes?
Answer: 4 packs.
Why it works: 3 packs give 18 boxes, 2 short, so you need a 4th pack and have 4 boxes left over.
A bike shop has 7 bikes. How many wheels are there?
Then ask: What if 2 of them were tricycles?
Answer: 14.
Why it works: Each bike has 2 wheels, and 7 × 2 = 14.
Double me, then add 3, and you get 15. What number am I?
Then ask: Why does working backward help here?
Answer: 6.
Why it works: Work backward: 15 − 3 = 12, and half of 12 is 6.
There are 3 cats, and each cat has 3 kittens. How many cats are there in all?
Then ask: Why is it easy to forget the mothers?
Answer: 12.
Why it works: 3 × 3 = 9 kittens, and the 3 mother cats make 12.
A week has 7 days. How many days are in 4 weeks?
Then ask: Is 4 weeks the same as a month? Why not?
Answer: 28.
Why it works: 7 × 4 = 28.
An egg carton holds 12 eggs in 2 equal rows. How many eggs are in each row?
Then ask: How else could you set out 12 eggs in equal rows?
Answer: 6.
Why it works: 12 eggs in 2 equal rows is 12 ÷ 2 = 6.
Money and time
A pencil costs 25 cents. How many pencils can you buy with one dollar?
Then ask: Which coins would you pay with?
Answer: 4.
Why it works: A dollar is 100 cents, and 25 + 25 + 25 + 25 = 100.
You have 3 dimes and 2 nickels. How much money is that?
Then ask: Can you make 40 cents a different way?
Answer: 40 cents.
Why it works: 3 dimes are 30 cents and 2 nickels are 10 cents, so 30 + 10 = 40.
It is 3 o'clock now. What time will it be in 10 hours?
Then ask: Will it be day or night then?
Answer: 1 o'clock.
Why it works: 3 + 10 = 13, but a clock starts over after 12, so 13 o'clock is 1 o'clock.
How many minutes are in an hour and a half?
Then ask: What do you do that takes about that long?
Answer: 90.
Why it works: An hour is 60 minutes and half an hour is 30, so 60 + 30 = 90.
Lemonade sells for 50 cents a cup, and you sell 6 cups. How much money did you take in?
Then ask: If the lemons and sugar cost $1, how much did you really earn?
Answer: $3.
Why it works: 6 cups at 50 cents is 300 cents, and 100 cents make a dollar, so that is $3.
You go to bed at 8 at night and wake up at 7 in the morning. How long did you sleep?
Then ask: How much sleep do you think kids your age need?
Answer: 11 hours.
Why it works: From 8 to 12 is 4 hours, and from 12 to 7 is 7 more, so 4 + 7 = 11.
A toy costs $7, and you pay with a $10 bill. How much change do you get?
Then ask: Which bills and coins could make that change?
Answer: $3.
Why it works: 10 − 7 = 3.
How many days are in a year that is not a leap year?
Then ask: How old is someone born on February 29, if you only count real birthdays?
Answer: 365.
Why it works: A regular year has 365 days. Every fourth year adds one more day, February 29.
Your birthday is 3 weeks and 2 days away. How many days is that?
Then ask: What would you do each day of the countdown?
Answer: 23.
Why it works: 3 weeks is 3 × 7 = 21 days, and 2 more make 23.
Which is more money, 5 quarters or 12 dimes?
Then ask: Did more coins mean more money here? Why not?
Answer: 5 quarters.
Why it works: 5 quarters are $1.25 and 12 dimes are $1.20, so the quarters win by 5 cents.
Shapes and patterns
I have 3 sides and 3 corners. What shape am I?
Then ask: What shape has 6 sides? Where have you seen one?
Answer: A triangle.
Why it works: Tri means three, the same as in tricycle.
What comes next: 2, 4, 6, 8…?
Then ask: Can you make a pattern that counts by 5s?
Answer: 10.
Why it works: Each number is 2 more than the one before it.
What comes next: 1, 2, 4, 8…?
Then ask: How many more steps until you pass 100?
Answer: 16.
Why it works: Each number is double the one before it, and 8 + 8 = 16.
How many corners does a box have?
Then ask: How many edges does it have? Count them on a real box.
Answer: 8.
Why it works: A box has 4 corners on the bottom and 4 on top, so 4 + 4 = 8.
A square garden has 4 sides, each 3 steps long. How many steps does it take to walk all the way around?
Then ask: What if the garden were a triangle with the same sides?
Answer: 12.
Why it works: 4 sides × 3 steps = 12 steps.
What comes next: 1, 1, 2, 3, 5, 8…?
Then ask: Can you find the two numbers after that?
Answer: 13.
Why it works: Each number is the two before it added together, and 5 + 8 = 13.
I have no corners and no straight sides. What shape am I?
Then ask: What around you right now is a circle?
Answer: A circle.
Why it works: A circle is one curved line, so it has no corners and no straight sides.
You cut a square from one corner to the opposite corner. How many triangles do you get?
Then ask: What if you cut along both of those lines?
Answer: 2.
Why it works: The cut runs across the middle and splits the square into 2 triangles.
What comes next: 1, 4, 9, 16…?
Then ask: Why are these called square numbers? Try drawing them with dots.
Answer: 25.
Why it works: These are numbers times themselves: 1 × 1, 2 × 2, 3 × 3, 4 × 4, so next comes 5 × 5 = 25.
How many sides do two triangles and a square have in all?
Then ask: Which shapes could you put together to get exactly 12 sides?
Answer: 10.
Why it works: Each triangle has 3 sides and the square has 4, so 3 + 3 + 4 = 10.
Trick math riddles
I am an odd number. Take away one letter and I become even. What number am I?
Then ask: What made you start thinking about numbers instead of letters?
Answer: Seven.
Why it works: Take the s off seven and you get even.
There are 12 fish in a tank, and half of them drown. How many fish are left?
Then ask: What other riddle tricks you with a fact instead of a number?
Answer: 12.
Why it works: Fish live in water and can't drown, so all 12 are still there.
How can you add eight 8s and get 1,000?
Then ask: Can you check it on paper?
Answer: 888 + 88 + 8 + 8 + 8 = 1,000.
Why it works: 888 + 88 = 976, and 976 + 8 + 8 + 8 = 1,000. Count the 8s: there are eight.
What is half of 2 plus 2?
Then ask: How would you write it so nobody argues?
Answer: 3, or 2.
Why it works: Half of 2 is 1, and 1 + 2 = 3. If you mean half of 2 + 2, that is half of 4, which is 2, so the way you say it changes the answer.
A rope ladder hangs over the side of a boat with 10 rungs above the water. The tide rises 3 feet. How many rungs are above the water now?
Then ask: What would change if the ladder hung from a dock?
Answer: Still 10.
Why it works: The boat floats, so it rises with the water, and the ladder rises with the boat.
What do you get if you multiply all the numbers on a phone keypad?
Then ask: Did you start multiplying before you noticed?
Answer: 0.
Why it works: One of the keys is 0, and anything times 0 is 0.
If two's company and three's a crowd, what are four and five?
Then ask: Can you make up a riddle that hides a sum?
Answer: 9.
Why it works: It sounds like a question about people, but 4 + 5 = 9.
Which weighs more, a pound of feathers or a pound of rocks?
Then ask: Which would you rather carry, and why?
Answer: Neither.
Why it works: A pound is a pound. Rocks are heavier for their size, but here there is the same weight of each.
A brick weighs 1 pound plus half a brick. How much does a whole brick weigh?
Then ask: Can you draw it so it's easier to see?
Answer: 2 pounds.
Why it works: A whole brick is half a brick plus 1 pound, so the other half must weigh 1 pound. Two halves of 1 pound make 2 pounds.
When I was 6, my sister was half my age. Now I am 10. How old is my sister?
Then ask: Why isn't the answer 5?
Answer: 7.
Why it works: When I was 6, she was 3, so she is 3 years younger. Now that I'm 10, she is 10 − 3 = 7.