The number of ways 
of finding a subrectangle with an 
rectangle can be computed by counting the number of ways in which the upper right-hand corner can be selected for a given lower left-hand corner. For a lower left-hand corner with coordinates 
, there are 
possible upper right-hand 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.
