Consecutive sides of all parallelograms are not perpendicular. Although any side of a parallelogram may be called a base, the altitude of a parallelogram is not always a side of the figure. In ABCD, AB is the base and DE is an altitude drawn to AB. The formula to find the area of a parallelogram may be derived as follows:
(figure available in print form)
Area of a Parallelogram = Base x Altitude or A=bh
Find the area of a parallelogram whose base is 8 1/2 inches and whose altitude is 15 1/4 inches in length.
Area= 8 1/2 x 15 1/4 = 17/2 x 61/4= 1437/8 = 179 5/8 sq. in.