There is a grid of 20 squares by 10 squares. How many different rectangles are possible?
(Note that square is a rectangle).

(In reply to solution by retiarius)

This is probably a silly question, but in the counting diagonals method, aren't you connecting four diagonals for each rectangle? i.e. from (0,0) to (1,1), (1,1) to (0,0), (0,1) to (1,0) and (1,0) to (0,1)? How come the answer is divided by two and not four?

Posted by Sam on 2004-01-21 11:40:06