7.2 Length, Area, and Volume 421 To determine the area, A, of a square, we use the formula A s ,2 = where s is the length of a side of the square. The area can also be determined by the formula area side side. = × We use this information in Example 3. Example 3 Converting Square Meters to Square Centimeters A square meter is how many times larger than a square centimeter? Solution A square meter is a square whose sides are 1 meter long. Since 1 m equals 100 cm, we can replace 1 m with 100 cm (see Fig. 7.5). The area of 1 m 1 m 1 m 100 cm 100 cm 10 000 cm . 2 2 = × = × = Thus, the area of one square meter is 10,000 times larger than the area of one square centimeter. This technique can be used to convert from any square unit to a different square unit. 7 Now try Exercise 53 100 cm 1 m 1 m2 or 10 000 cm2 100 cm 1 m 100 cm 100 cm 1 m 1 m Figure 7.5 Example 4 Tabletop Determine the area of a rectangular tabletop if its length is 1.5 m and its width is 1.1 m (see Fig. 7.6). Solution To determine the area, we use the formula Area length width = × or A l w = × Substituting values for l and w, we have = × = A 1.5 m 1.1 m 1.65 m2 Notice that the area is measured in square meters. 7 Now try Exercise 67 1.1 m 1.5 m Figure 7.6 Example 5 Face of a Clock The face of a circular clock has a diameter of 36 cm. Determine the surface area of the face of the clock. Solution The formula for determining the area of a circle is π = A r ,2 where π is approximately 3.14. The radius, r, is one-half the diameter. Since the diameter is 36 cm, the radius is 18 cm. Using the π key on a calculator we get the following. π π = = ≈ A r A A (18) 1017.88 cm 2 2 2 Thus, the area of the face of the clock is approximately 1017.88 cm .2 7 Now try Exercise 71 Timely Tip The number π was introduced in Chapter 5. Recall that π is ap- proximately 3.14. However, when solving problems we will use the π key on a scientific calculator to get a more accurate answer. Dimedrol68/Shutterstock
RkJQdWJsaXNoZXIy NjM5ODQ=