The diagram shows one way to develop the formula for the area of a circle Pieces of a circle with radius rare rearranged to create a shape that resembles a parallelogram Since the circumference of the circle can be represented by 27 and the area of a parallelogram is determined using A bh which represents the approximate area of the parallelogram like figure O A 27 r O A 2 r 2 A 2 r 1 A 3 2 r