If you square me, I am equal to the sum of all odd positive integers from 1 up to 19. What positive number am I?
10
The sum of the first N odd numbers is N^2. There are 10 odd numbers from 1 to 19 (1, 3, ..., 19). Their sum is 100, and sqrt(100) = 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: Hard. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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