Derive the formula A = (base)(height).

To derive the formula for the area of a parallelogram moving a piece of the parallelogram so as to make a rectangle with the same area. Start with a parallelogram with known base length (width) w and altitude h (height). Cut off a triangular section. Translate (move) the copy to touch the original so as to create a rectangle. This rearranging has created a rectangle whose area is clearly the same as the original parallelogram. Recall that the area of a rectangle is found by multiplying its width times its height. The area of the original parallelogram is therefore area of parallelogram is A=w*h where w is the width, or length of a base, and h is the altitude (height) of the parallelogram.