The number of ways of finding a subrectangle with an rectangle can be computed by counting the number of ways in which the upper righthand corner can be selected for a given lower lefthand corner. For a lower lefthand corner with coordinates , there are possible upper righthand corners, so
(1)
 
(2)

Equivalently, is the number of ways of picking two lines out of sets of and lines, giving
(3)
 
(4)

as before. Particular tilings are shown above for and rectangles.