This Simple Maths 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 1’s and -1’s can give three different answers.

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]