If you multiply me by myself, add the number of sides on a standard die, and then subtract my original self, the result is 36. What number am I?
6
Let the number be x. The equation is x^2 + 6 - x = 36, which simplifies to x^2 - x - 30 = 0. Factoring gives (x - 6)(x + 5) = 0. Since positive numbers are standard for these riddles, x = 6. (Check: 6*6 = 36; 36 + 6 = 42; 42 - 6 = 36).
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: Hard. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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