A rectangular stained glass window is made up of identical triangular parts as pictured below.
What is the area of the shaded triangular section?
Note that the width of each rectangle = 48 / 3 = 16 in
And the height of each rectangle = 36 / 4 = 9 in
So.....the area of each of these rectangles = 16 * 9 = 144 in^2
And the shaded area is 1/2 of this = 72 in^2