The length of each side of pentagonal church window with the perimeter of 60 inches is C. 12 inches. The perimeter (P) of a pentagon is the sum of its side lengths (s). Since pentagon has 5 sides, the perimeter of the pentagon is: P = 5s. If we know that the perimeter is 60 inches, the side length will be: 60 in = 5s. s = 60 in / 5. s = 12 in. The length of the side of the window is 12 inches.