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Berkeley City College

Pre-Algebra: Lesson 140

Lesson Description

Students learn that a parallelogram is a quadrilateral with two pairs of parallel sides, and the formula for the area of a parallelogram is base times height. For example, the area of a parallelogram that has a base of 13 inches and a height of 9 inches is 13 times 9, or 247 square inches. Students also learn that a trapezoid is a quadrilateral with one pair of parallel sides, and the formula for the area of a trapezoid is 1/2 times (base 1 + base 2) times height. For example, the area of a trapezoid that has bases of 10 centimeters and 12 centimeters and a height of 8 centimeters is 1/2 times (10 + 12) times 8, which simplifies to 1/2 times 22 times 8, or 11 times 8, which is 88 square centimeters.