in the chessboard, There are 9 horizontal lines and 9 vertical lines. Choose two distinct horizontal lines, and two distinct vertical lines. (any rectangle determines a pair of horizontal lines and a pair of vertical lines)
so # rectangle = 9C2 * 9C2 = 1296
u can see that there are 82 small 1×1 squares, 72 2×2 squares, and so on down to 12 1×1 squares,,, u need to add to find total # squres
so # squres = 12 + 22 + 32 + 42 + 52 + 62 + 72 + 82 = 204
number of rectangles in a chess board that are not sqaure = 1296 - 204 = 1092