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The no. of rectangles in a chess board is ?

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

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 = $^9C_2.^9C_2=36\times36=1296$

edited Dec 20, 2013