The no. of rectangles in a chess board is ?

Question

$\begin{array}{1 1} 64 \\ 648 \\ 1296 \\ 2592 \end{array}$

Answer 1

In a chess board there are 9 vertical lines and 9 horizontal lines.

To form a rectangle we need 2 vertical lines and two horizontal lines at a time.

$\therefore $ Total no. of rectangles = $^9C_2.^9C_2=36\times36=1296$