There's a 6 by 6 grid and you're asked to start on the top left corner. Now your aim is to get to the bottom right corner. You are only allowed to move either right or down. You must never move diagonally or backwards.
I figured out the way to do this through writing number of ways to reach each cell in a box and got the answer to be 252
However I saw a formula for questions of this type which gives answer as 12!/(6!*6!)
I would like to know why the above formula doesn't work in this case and preferably where it's applicable