Question

Find the number of rectangles in the adjoining figure(2 squares is also considered a rectangle):

Answer 1

The formula is:
12          6   
 ∑  n  ·  ∑  n =
 1           1
= ( 12 + 11 + 10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 ) · ( 6 + 5 + 4 + 3 + 2 + 1 ) =
= 78 · 21 = 1638 rectangles
Answer: C ) 1638