Definition/Procedure Example Area of a Rectangle The area of a rectangle is the size of the region enclosed in the fi gure. We can fi nd the area, A, of a rectangle using this formula: Area length width or A lw The units for area are square units. (p. 296) Find the area of the rectangle in the previous box in the Summary. A lw A (7 cm)(3 cm) Substitute the values. A 21 cm2 Multiply. Perimeter and Area of a Square A square is a rectangle with all four sides of equal length. The perimeter, P, of a square with side length s can be found using one of these formulas: 1) Perimeter side side side side 2) P 4 side 3) P 4 s The area, A, of a square with side length s can be found using one of these formulas: 1) Area side side 2) A s s 3) A s2 (p. 297) Find a) the perimeter and b) the area of this square. 1 ft 2 1 ft 2 a) Use P 4s. P 4 a 1 2 ftb Substitute the length of the side. P 2 ft Multiply. b) Use A s2. A a 1 2 2 Substitute the length of the side. ftb A 1 4 ft2 Area of a Parallelogram A parallelogram is a four-sided fi gure whose opposite sides are parallel and the same length. The area, A, of a parallelogram is Area base height or A bh where b the length of the base and h the height. The base is the side that forms a right angle with the height. (p. 299) Find the area of the parallelogram. 5 m 9 m A bh A (9 m)(5 m) Substitute the values. A 45 m2 Multiply. Area of a Trapezoid A trapezoid is a four-sided fi gure with exactly one pair of parallel sides. The area, A, of a trapezoid is A 1 2 height (short base long base) or A 1 2 h (b B) where h the height, b the length of the short base, and B the length of the long base. The bases are always the parallel sides. (p. 300) Find the area of the trapezoid. 4 in. 6 in. 2 in. A 1 2 h (b B) A 1 2 (2 in.)(4 in. 6 in.) Substitute the values. A 1 2 (2 in.)(10 in.) Add inside the parentheses. A 10 in2 Multiply. www.mhhe.com/messersmith CHAPTER 4 Summary 345
messersmith_power_prealgebra_1e_ch4_7_10
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