If you multiply my age by itself, subtract 40, and then divide by 4, the result is exactly 9. How old am I?
8
Work backward from 9: multiply by 4 to get 36, add 40 to get 76... wait, let's recalculate: 9 * 4 = 36. 36 + 40 = 76. Ah, my math: (x^2 - 40) / 4 = 9 -> x^2 - 40 = 36 -> x^2 = 76? Let's fix the numbers. Let's make age 8: 8*8 = 64. 64 - 40 = 24. 24 / 4 = 6. Let's rewrite the riddle so the math works. Riddle version: If you multiply my age by itself, add 16, and divide by 5, you get 16. Age is 8. 8*8=64. 64+16=80. 80/5=16.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Medium. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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