EXAMPLE 3 Latrice has a piece of fabric that is 1 m 20 cm long. She cuts off a piece that is 85 cm long. Find the length of fabric remaining, in centimeters. Solution Because Latrice cuts off an 85-cm piece of fabric, we have to subtract that from the total length of 1 m 20 cm. The units are not the same, so convert 1 m 20 cm to centimeters since we are asked to express the answer in centimeters. Change 1 m 20 cm to centimeters. 1 m 20 cm 100 cm 20 cm 120 cm Subtract 85 cm from 120 cm. 11 10 1 2 0 2 83 5 5 120 cm 2 85 cm 5 35 cm 35 cm of fabric remains. Check the answer by working backward. Amount of fabric remaining Amount of fabric cut off Original length of fabric 35 cm 85 cm 120 cm We can think of 120 cm as 100 cm 20 cm 1 m 20 cm. This is the same as the original length of fabric stated in the problem. YOU TRY 3 A carton of orange juice contains 1 L 450 mL. If Zach uses 600 mL, how many milliliters of orange juice is left in the carton? When we are working with problems involving money, round answers to the nearest cent. EXAMPLE 4 At the deli, prosciutto costs $48.99/kg. Giovanni needs 120 g for a chicken saltimbocca recipe. How much will the prosciutto cost? Solution The $48.99 per kilogram is the unit cost of the prosciutto. To fi nd the cost of 120 g of prosciutto, we have to multiply the unit cost by the amount of prosciutto Giovanni is buying. First, however, we have to change 120 g to kilograms so that the units are the same. To change 120 g to kilograms, use either unit fractions or the metric conversion chart. We will use unit fractions. Then, use unit fractions to fi nd the cost. Change 120 g to kilograms. 120 g 1 1 kg 1000 g 120 kg 1000 0.120 kg 0.12 kg Find the cost of the prosciutto. Multiply the amount of prosciutto by the unit cost. 0.12 kg 1 $48.99 kg $5.8788 $5.88 Giovanni spent $5.88 for 120 g of prosciutto. 600 CHAPTER 7 Measurement and Conversion www.mhhe.com/messersmith
messersmith_power_prealgebra_1e_ch4_7_10
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