If you multiply me by myself, add the number you started with, and then subtract the original number, you get 100. What number am I?
10 or -10
Let the number be x. Multiplying by itself gives x^2. Adding the original number gives x^2 + x. Subtracting the original number leaves x^2 = 100. Therefore, x can be 10 or -10.
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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