42 Chapter 1 Whole Numbers The 3-cm by 2-cm region in Figure 1-4 suggests that to find the area of a rectangle, multiply the length by the width. If the area is represented by A, the length is represented by l, and the width is represented by w, then we have Area of rectangle 1length2 1width2 The letters A, l, and w are variables because their values vary as they are replaced by different numbers. Finding the Area of a Rectangle Example 10 Find the area and perimeter of the rectangle. Solution: Area: A l w A 17 yd2 14 yd2 28 yd2 Recall from Section 1.3 that the perimeter of a polygon is the sum of the lengths of the sides. In a rectangle the opposite sides are equal in length. Perimeter: P 7 yd 4 yd 7 yd 4 yd 22 yd 28 yd2 The area is and the perimeter is 22 yd. Finding Area in an Application Example 11 The state of Wyoming is approximately the shape of a rectangle (Figure 1-5). Its length is 355 mi and its width is 276 mi. Approximate the total area of Wyoming by rounding the length and width to the nearest ten. A l w 4 yd 7 yd 7 yd 4 yd 4 yd 7 yd 12 ft 5 ft Answers 14. Area: 60 ft2; perimeter: 34 ft 15. 20,000 ft2 WY 276 mi 355 mi Figure 1-5 Solution: 355 rounds to 276 rounds to 1 3 4 6 0 28 0 288 720 1008 00 The area of Wyoming is approximately 100,800 mi2. Skill Practice 14. Find the area and perimeter of the rectangle. Avoiding Mistakes Notice that area is measured in square units (such as yd2) and perimeter is measured in units of length (such as yd). It is important to apply the correct units of measurement. Skill Practice 15. A house sits on a rectangular lot that is 192 ft by 96 ft. Approximate the area of the lot by rounding the length and width to the nearest hundred.
miller_prealgebra_2e_ch1_3
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