35 Mathematical Riddles with Answers

Here are all 35 mathematical riddles combined, along with their answers:

1. What’s a number you get when you subtract 10 from 100?
   Answer: 90
2. What has four sides but isn’t a square?
   Answer: A rectangle
3. What’s the square root of 144?
   Answer: 12
4. If two’s company, what’s three?
   Answer: A crowd
5. What number is 7 less than 100?
   Answer: 93
6. What’s half of 8?
   Answer: 4 (or two zeros)
7. What comes once in a minute, twice in a moment, but never in a thousand years?
   Answer: The letter ‘M’
8. How many months have 28 days?
   Answer: All 12 months!
9. What is the smallest positive number that is divisible by all numbers from 1 to 6?
   Answer: 60
10. I’m an odd number. Take away one letter, and I become even. What am I?
    Answer: Seven (remove ‘s’ to make “even”)
11. How many times can you subtract 5 from 25?
    Answer: Once, because after that, it’s no longer 25.
12. What number do you get when you multiply all the numbers on a phone’s keypad?
    Answer: 0 (because of the 0 on the keypad)
13. A clock shows the time as 3:15. What is the angle between the hour and minute hands?
    Answer: 7.5 degrees
14. What’s the next number in the sequence: 2, 6, 12, 20, ?
    Answer: 30 (difference increases by 2 each time)
15. If there are 5 apples and you take away 3, how many do you have?
    Answer: 3 (because you took them)
16. What is the sum of the angles in a triangle?
    Answer: 180 degrees
17. What three positive numbers give the same answer when multiplied and added together?
    Answer: 1, 2, and 3
18. If you have two coins totaling 30 cents, and one is not a nickel, what are the coins?
    Answer: A quarter and a nickel (because one isn’t a nickel).
19. What is a number that is the same forwards and backwards?
    Answer: A palindrome (e.g., 121).
20. If a plane crashes on the border of the U.S. and Canada, where do they bury the survivors?
    Answer: Nowhere; survivors aren’t buried.
21. How many seconds are there in a year?
    Answer: 12 (January 2nd, February 2nd, etc.).
22. What is always coming but never arrives?
    Answer: Tomorrow
23. If there are six apples and you take away four, how many do you have?
    Answer: Four, because you took them.
24. Which weighs more, a pound of feathers or a pound of bricks?
    Answer: They weigh the same!
25. What’s the number that’s one more than a hundred but one less than a thousand?
    Answer: 999
26. If two is company and three’s a crowd, what’s four and five?
    Answer: Nine
27. If five cats can catch five mice in five minutes, how many cats are needed to catch 100 mice in 100 minutes?
    Answer: Five (each cat catches one mouse every five minutes).
28. How many times can you divide 50 by 2?
    Answer: Once, because after dividing, it’s no longer 50.
29. I am an odd number. Take away one letter, and I become even. What am I?
    Answer: Seven (remove “s” to get “even”).
30. How many zeros are in a trillion?
    Answer: Twelve zeros
31. If a train travels 100 miles in 1 hour, how long does it take to travel 50 miles?
    Answer: 30 minutes
32. Which number is missing from this series: 2, 4, 8, 16, __?
    Answer: 32
33. What comes once in a minute, twice in a moment, but never in a thousand years?
    Answer: The letter “M”
34. What is a three-digit number where the sum of its digits is 12, the first digit is twice the second, and the second is three times the third?
    Answer: 642
35. How many letters are in the alphabet?
    Answer: 11 (The word “alphabet” has 11 letters).