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 Step 1: Read the problem carefully, and restate it in your own words. Giovanni has to buy 120 g of prosciutto. It costs $48.99/kg. We must determine how much the prosciutto will cost. Step 2: Make a plan. Underline important words in our restatement of the problem in Step 1. 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. Plan: Change 120 g to kilograms. Then, multiply that number by the unit cost, $48.99/kg, to fi nd the cost of the prosciutto. Step 3: Solve the problem. 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 Step 4: State the answer in a complete sentence. Giovanni spent $5.88 for 120 g of prosciutto. Step 5: Check the answer. Work backward. Divide $5.88 by 0.12 kg to get the unit cost. $5.88 0.12 kg $49.00/kg. This is close to the given unit cost of $48.99/kg. The difference is due to the rounding of the cost of the prosciutto in Step 3. YOU TRY 4 In the bulk foods section of the grocery store, lentils cost $3.49/kg. If Devyani buys 640 g, how much does she pay? EXAMPLE 5 On a production line, 280 L of shampoo is divided evenly into 800 bottles. How many milliliters of shampoo is in each bottle? Solution Step 1: Read the problem carefully, and restate it in your own words. 280 L of shampoo is divided evenly into 800 bottles. We must determine the number of milliliters of shampoo in each bottle. 468 CHAPTER 7 Measurement and Conversion www.mhhe.com/messersmith
messersmith_power_basic_college_1e_ch4_7_10
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