This Simple Math Puzzle Will Melt Your Brain

Adding and subtracting ones sounds simple, right? Not according to the old Italian mathematician Grandi—who showed that a simple addition of 1s and -1s can give three different answers.

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Wait, what? If that sounds like it makes no sense that's because... well, it doesn't really. But better let Dr James Grime explain it to you rather than me. Prepare to scratch your head. [YouTube]

DISCUSSION

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SkipErnst

When he took 1 - 1 + 1 - 1 + 1 ... and added the parens here 1 (- 1 + 1) (- 1 + 1) ... I was cool with it. But then he added more pluses between them 1 + (- 1 + 1) + (- 1 + 1) and I felt like that was an error. I thought two numbers next to each other implied a multiplication. E.g., 1 * (- 1 + 1) * (- 1 + 1). That ends up being a result of 0 again, not 1.

But whatever. I'll trust the mathematicians.