Math riddles are short puzzles that hide a number problem inside a story or a trick. You solve them with logic, careful reading and a little arithmetic. Below are 40 math riddles with answers, sorted from easy to hard, and each one comes with a hint and a short explanation.
Most people search for math riddles for one of two reasons. Either you want a quick brain workout, or you need something fun for a kid, a class or a family dinner. In both cases, you need riddles that are clear, fair and easy to check.
You’re in the right place if you want puzzles you can solve without a calculator. First, start with the easy math riddles, and then work up to the hard ones. Want a wider mix? Try our tricky riddles with answers, share kids riddles with younger players, or, after you finish here, test yourself on hard riddles and 80 adult riddles with answers.
Easy Math Riddles to Warm Up
These easy math riddles need nothing more than careful reading. A pencil is optional, and you probably won’t need one.
Easy Math Riddles for Beginners (1–4)
1. There are 5 apples. You take away 3. How many apples do you have?
Hint: Ask who is holding the apples now.
Answer: 3.
Explanation: Because you took 3, you hold 3. The 2 left behind aren’t yours.
2. Which weighs more: a pound of feathers or a pound of bricks?
Hint: Look at the unit, not the objects.
Answer: They weigh the same.
Explanation: A pound is a pound, so the weight is equal. Feathers just take up more room.
3. I’m an odd number. Take away one letter and I become even. What number am I?
Hint: Spell the number out.
Answer: Seven.
Explanation: Simply drop the “s” from “seven,” and “even” is left.
4. How many months have 28 days?
Hint: Think “at least.”
Answer: All 12.
Explanation: February has 28 days, and every other month has more. Therefore, each month has at least 28.
Easy Math Riddles With Number Twists (5–8)
5. How many times can you subtract 5 from 25?
Hint: Watch what the number becomes after the first try.
Answer: Once.
Explanation: After one subtraction you have 20. After that, you’re subtracting from 20, not 25.
6. I’m a number. Double me, add 4, and you get 14. What number am I?
Hint: Work backward from 14.
Answer: 5.
Explanation: First, take away 4 to get 10. Then halve it. To check, 5 doubled is 10, and 10 plus 4 is 14.
7. Name three whole numbers that give the same answer when you add them or multiply them.
Hint: Start with the smallest counting number.
Answer: 1, 2 and 3.
Explanation: 1 + 2 + 3 = 6. Likewise, 1 × 2 × 3 = 6.
8. A farmer has 17 sheep. All but 9 run away. How many sheep are left?
Hint: Focus on the words “all but.”
Answer: 9.
Explanation: “All but 9” means 9 stayed put. So the 17 is just a distraction.
Tricky Math Riddles With Answers
Here the math riddles start to bite. Each one has an obvious answer that feels right and is wrong, so slow down before you commit.
Tricky Math Riddles With Money and Time (9–13)
9. Can you make 1,000 by adding eight 8s?
Hint: Some of the 8s can sit side by side.
Answer: 888 + 88 + 8 + 8 + 8 = 1,000.
Explanation: The first two numbers use five 8s and total 976. Then the last three 8s add 24.
10. Two U.S. coins add up to 30 cents. One of them is not a nickel. What are the coins?
Hint: “One isn’t a nickel” doesn’t mean “neither is.”
Answer: A quarter and a nickel.
Explanation: The quarter is the coin that isn’t a nickel. However, the other coin is a nickel.
11. A clock takes 5 seconds to strike 6 times. How long does it take to strike 12?
Hint: Count the gaps, not the strikes.
Answer: 11 seconds.
Explanation: Six strikes have 5 gaps, so each gap lasts 1 second. Likewise, twelve strikes have 11 gaps.
12. A patch of lily pads doubles every day and covers a pond on day 48. On which day did it cover half the pond?
Hint: Think about what doubling means.
Answer: Day 47.
Explanation: Because the patch doubles each day, half the pond on day 47 becomes the whole pond on day 48.
13. A bat and a ball cost $1.10 together. The bat costs $1.00 more than the ball. How much is the ball?
Hint: Test 10 cents first and check the total.
Answer: 5 cents.
Explanation: A 10-cent ball makes the bat $1.10 and the total $1.20. Instead, a 5-cent ball gives a $1.05 bat and a $1.10 total.
Tricky Math Riddles With Ages and Counting (14–18)
14. A mother is four times as old as her daughter. In 20 years she’ll be twice as old. How old is the daughter now?
Hint: Call the daughter’s age x and the mother’s 4x.
Answer: 10.
Explanation: The mother is 40 now. In 20 years, then, they’ll be 60 and 30, and 60 is twice 30.
15. A snail climbs 3 feet up a 10-foot well each day and slides back 2 feet each night. On which day does it reach the top?
Hint: Look at the last day separately.
Answer: Day 8.
Explanation: After 7 days and nights, the snail sits at 7 feet. Then on day 8 it climbs 3 more and escapes before it can slide back.
16. A doctor gives you 3 pills and says to take one every 30 minutes. How long do the pills last?
Hint: You take the first pill right away.
Answer: 1 hour.
Explanation: You take pills at 0, 30 and 60 minutes. So there are only two gaps.
17. How many times does the digit 9 appear in the numbers from 1 to 100?
Hint: Count the tens place and the ones place.
Answer: 20.
Explanation: Ten numbers end in 9 (9, 19, up to 99). Also, ten start with 9 (90 to 99). Together they make 20, and 99 counts twice because it has two 9s.
18. Five cats catch five mice in five minutes. How many cats do you need to catch 100 mice in 100 minutes?
Hint: Find how fast one cat works.
Answer: 5 cats.
Explanation: Each cat catches 1 mouse every 5 minutes. So in 100 minutes, each cat catches 20 mice, and 5 cats catch 100.
Hard Math Riddles for Adults
These hard math riddles reward patience. Most of them lean on classic ideas from counting, number patterns and probability.
Hard Math Riddles With Counting (19–23)
19. Ten people at a party each shake hands with every other person once. How many handshakes happen?
Hint: Each handshake involves two people.
Answer: 45.
Explanation: Ten people times 9 others gives 90. However, every handshake got counted twice, so halve it.
20. What is 1 + 2 + 3 + … + 100?
Hint: Pair the first number with the last.
Answer: 5,050.
Explanation: 1 + 100, 2 + 99 and 3 + 98 each make 101. Overall, there are 50 pairs, and 50 × 101 is 5,050.
21. Two siblings’ ages add up to 20 and multiply to 96. How old are they?
Hint: List pairs that add to 20.
Answer: 8 and 12.
Explanation: 8 + 12 = 20, and also 8 × 12 = 96.
22. How many squares of any size sit on a standard 8-by-8 chessboard?
Hint: Don’t stop at the 64 small ones.
Answer: 204.
Explanation: Add up the squares by size: 64 + 49 + 36 + 25 + 16 + 9 + 4 + 1. In other words, the total is 204.
23. What is the smallest positive number that every whole number from 1 to 10 divides evenly?
Hint: Look for the biggest power of each prime.
Answer: 2,520.
Explanation: You need 8 (for 2, 4 and 8), 9 (for 3, 6 and 9), 5 and 7. Then multiply them: 8 × 9 × 5 × 7 = 2,520.
Hard Math Riddles With Big Numbers and Odds (24–27)
24. What is the last digit of 7 to the power of 100?
Hint: Write out the first few powers of 7.
Answer: 1.
Explanation: The last digits cycle 7, 9, 3, 1 and then repeat. Since 100 is a multiple of 4, it lands on 1.
25. How many zeros sit at the end of 100 factorial (100 × 99 × 98 × … × 1)?
Hint: Each zero needs a 5 and a 2.
Answer: 24.
Explanation: Twos are plentiful, so count the fives. There are 20 multiples of 5 up to 100, plus 4 extra from the multiples of 25.
26. How many people must be in a room before two of them are more likely than not to share a birthday?
Hint: Count pairs of people, not people.
Answer: 23.
Explanation: Twenty-three people form 253 pairs. As a result, the chance of a match passes 50% (assuming evenly spread birthdays and ignoring February 29). For the full math, see the birthday problem.
27. You pick door 1 of 3, and one door hides a car. The host, who knows where it is, opens door 3 to show a goat. Should you switch to door 2?
Hint: Your first pick was right only 1 time in 3.
Answer: Yes. Switching wins about two-thirds of the time.
Explanation: Your first choice holds the car 1 time in 3. Then the host’s reveal pushes the other 2-in-3 chance onto the one door left. For more, read about the Monty Hall problem.
Number Pattern Math Riddles
Pattern math riddles ask what comes next. Therefore, look for the rule first, and then apply it.
Number Pattern Math Riddles With Sequences (28–31)
28. What comes next: 1, 1, 2, 3, 5, 8, ?
Hint: Look at the two numbers before each one.
Answer: 13.
Explanation: Each number is the sum of the previous two, so 5 + 8 = 13. Mathematicians call this the Fibonacci sequence.
29. What comes next: 2, 6, 12, 20, 30, ?
Hint: Check the gaps between numbers.
Answer: 42.
Explanation: The gaps grow by 2 each time (4, 6, 8, 10). Therefore, the next gap is 12.
30. What comes next: 1, 4, 9, 16, 25, ?
Hint: Think of squares.
Answer: 36.
Explanation: These are 1², 2², 3², 4² and 5². Next comes 6².
31. What comes next: 1, 11, 21, 1211, 111221, ?
Hint: Read each number out loud.
Answer: 312211.
Explanation: Each term describes the one before it. For example, 111221 reads as “three 1s, two 2s, one 1,” which gives 312211.
Number Pattern Math Riddles With Word Clues (32–34)
32. If one = 3, two = 3, three = 5, four = 4 and five = 4, what does six equal?
Hint: Count letters.
Answer: 3.
Explanation: Each number equals the letters in its spelling. Likewise, “six” has 3 letters.
33. What comes next: 31, 28, 31, 30, 31, ?
Hint: Think of a calendar.
Answer: 30.
Explanation: These are the days in January through May. So June comes next with 30.
34. I’m a three-digit number under 200. My tens digit is four times my ones digit, and my hundreds digit is 3 less than my tens digit. What number am I?
Hint: Try 1 for the ones digit.
Answer: 141.
Explanation: A ones digit of 1 gives a tens digit of 4 and a hundreds digit of 1. However, larger options like 582 break the “under 200” rule.
Funny Math Riddles
Finally, here are a few funny math riddles to reward your brain for all that effort. Because they’re jokes, there’s no math to check, only groans to enjoy.
35. Why was 6 afraid of 7?
Answer: Because 7 ate 9.
36. What did zero say to eight?
Answer: Nice belt!
37. What is a math teacher’s favorite season?
Answer: Sum-mer.
38. What do you call a number that can’t stand still?
Answer: A roamin’ numeral.
39. Why was the math book so sad?
Answer: It had too many problems.
40. Why was the equal sign so humble?
Answer: It knew it wasn’t less than or greater than anyone else.
How to Solve Math Riddles Faster
Good solvers follow the same short routine on almost every one of these math riddles.
- Read it twice. Most wrong answers come from skimming.
- Circle the trigger words. Phrases like “all but,” “more than” and “one of them isn’t” change the whole problem.
- Write down what you know. A quick note such as “total $1.10, difference $1.00” often reveals the path.
- Test the obvious answer. If it fails the check, you’ve found the trap.
- Check your answer against every clue. Then say it out loud.
For example, take the bat and ball. The obvious answer is 10 cents, but that makes the total $1.20. Only 5 cents gives a $1.05 bat and a $1.10 total.
FAQ
What is the difference between a math riddle and a math problem?
A math problem states exactly what to find. A math riddle, however, wraps the same thinking in a story or a trick, so careful reading matters as much as the arithmetic.
What age are math riddles good for?
Children around age 7 can enjoy counting and trick riddles. Meanwhile, the algebra, number theory and probability puzzles suit teens and adults.
Can I use math riddles in class or at home?
Yes. Use one as a two-minute warm-up and let people argue for their answers before you reveal it. Also, wrong guesses make the explanation stick.
Do I need a calculator for math riddles?
No. Nearly all of them work in your head or on paper. Even the hard ones, like the last digit of 7 to the power of 100, rely on a pattern rather than a calculator.
Conclusion
You came for math riddles you could solve and check, and now you have 40 of them, from easy warm-ups to hard puzzles with real reasoning behind them. When you get stuck, go back to the five-step routine. Read twice, spot the trigger words, write down what you know, test the obvious answer, and then check your result. The traps are the fun part, and each one you spot makes the next riddle easier.
More to Try
Hungry for more? Browse these riddles for adults, pass the fun to the riddles for kids page, or take on the hard riddles with answers when you’re feeling brave.
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