In the "proof" presented, the series 1-1+1... is "shown" to equal to 1/2 by a particular choice of interleaving of the values in the series. But with other methods of interleaving, the sum can be made to "equal" 0, 1 1/3 or indeed AFAICT *any rational number between 0 and 1*.

So... why is the particular interleaving that gives 1/2 as the answer "correct"?

*3 points [-]