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# 25 Math Riddles Only the Smartest Can Get Right

1. What starts with an E, ends with an E, but only contains one letter? Answer: An envelope.…

1. What starts with an E, ends with an E, but only contains one letter? Answer: An envelope.

2. What number do you get when multiplying the numbers on a telephone’s number pad? Answer: Zero (because one of the numbers is zero).

3. I am an odd number. Take away a letter, and I become even. What number am I? Answer: Seven (take away the “s” and it becomes “even”).

4. What is the following number in the sequence: 1, 11, 21, 1211, 111221, 312211, …? Answer: 13112221 (the sequence describes the last number, so the next one is “one three, one one, two two, two one”).

5. If two’s company and three’s a crowd, what are four and five? Answer: Nine (the sum of the numbers).

6. What is the sum of all numbers on a roulette wheel? Answer: 666 (the numbers on a roulette wheel add up to 666).

7. What is the smallest positive number divisible by all the numbers from 1 to 10? Answer: 2520.

8. What is the following number in the sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, …? Answer: 34 (the sequence is the Fibonacci sequence, where each number is the sum of the previous two).

9. What is the following number in the sequence: 1, 2, 6, 42, 1806, …? Answer: 3263442 (the sequence is the product of each number and the previous one plus one).

10. What is the only number that, when written out, has its letters in alphabetical order? Answer: Forty.

11. What is the missing number in the sequence: 9, 16, 23? 37, 44, 51, 58, 65? Answer: 30 (the sequence adds 7 to each number, except for the missing one).

12. What is the next number in the sequence: 2, 6, 18, 54, …? Answer: 162 (the sequence multiplies each number by 3).

13. What is the missing number in the sequence: 3, 8, 15, 24? 48? Answer: 35 (the sequence adds 5, then 7, then 9, etc.).

14. What is the following number in the sequence: 3, 8, 18, 38, …? Answer: 78 (the sequence doubles each number, then adds 2).

15. What is the following number in the sequence: 1, 2, 4, 8, 16, …? Answer: 32 (the sequence doubles each number).

16. What is the next number in the sequence: 1, 4, 27, 256, …? Answer: 3125 (the sequence is the nth power of n, so the following number is 5 to the power of 5).

17. What is the missing number in the sequence: 2, 5, 10, 17? 37? Answer: 26 (the sequence adds 3, then 5, then 7, etc.).

18. What is the following number in the sequence: 7, 12, 18, 25, 33, …? Answer: 42 (the sequence adds 5, then 6, then 7, etc.).

19. If you have two coins that add up to 30 cents, and one is not a nickel, what are the two coins? Answer: A quarter and a nickel (if one was a nickel, the other coin would have to be a dime, which would only add up to 15 cents).

20. What is the following number in the sequence: 1, 3, 6, 10, 15, …? Answer: 21 (the sequence adds 2, then 3, then 4, etc.).

21. What is the missing number in the sequence: 5, 10, 19, 34? 85? Answer: 59 (the sequence adds 5, then 9, then 15, etc.).

22. What is the following number in the sequence: 1, 3, 9, 27, 81, …? Answer: 243 (the sequence is the nth power of 3, so the following number is 3 to the power of 5).

23. What is the following number in the sequence: 2, 5, 10, 17, 26, …? Answer: 37 (the sequence adds 3, then 5, then 7, etc.).

24. What is the missing number in the sequence: 4, 9, 19, 39? 159? Answer: 79 (the sequence doubles each number, then adds 1).

25. What is the following number in the sequence: 1, 4, 10, 22, 46, …? Answer: 94 (the sequence doubles each number, then adds 2).

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