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Parallelograms: Area and Perimeter

A parallelogram is a quadrilateral in which both pairs of opposite sides are parallel .

It can be shown that opposite sides of parallelogram must be congruent , that opposite angles are also congruent , and that consecutive angles are supplementary .

The area A of a parallelogram is given by the formula

A = b h ,

where b is the length of one base and h is the height. (The figure below shows how to find the height of a parallelogram.)

The perimeter of a parallelogram is the sum of the lengths of its four sides.

For example, in the figure below, if P Q R S is a parallelogram, then we know opposite sides are congruent, so P Q = 10 and P S = 6 .

Therefore, the perimeter is 6 + 10 + 6 + 10 or 32 cm.