Look at Example 1. If we had tried to multiply 400 m by the unit fraction 400 m relating meters and yards as 1 0.91 m 1 yd , the units of meters would not divide out. That’s how we know this is the wrong way to do this problem! If this happens the first time you try to convert between units, don’t panic. Write the unit fraction the other way to see whether the correct units will divide out. Let’s convert between other units. EXAMPLE 2 Convert to the indicated unit. Round the answer to the nearest tenth, if necessary. a) A recipe calls for 2 kg of beef stew meat. Convert this number to pounds. b) Huong wants to buy a 50 - in. plasma television. Convert this number to centimeters. Solution a) We are given kilograms and want to convert to pounds. The relationship is 1 lb 0.45 kg Multiply 2 kg by the unit fraction relating kilograms and pounds so that kilograms will divide out and leave us with pounds. 2 kg 1 lb 0.45 kg 2 kg 1 1 lb 0.45 kg Divide out the unit of kilograms. 2 lb 0.45 Multiply. 4.4 lb Divide. Therefore, 2 kg of beef 4.4 lb. b) We are given inches and want to convert to centimeters. The relationship is 1 in. 2.54 cm Because this is an exact conversion, we use instead of . Multiply 50 in. by the unit fraction relating inches and centimeters so that inches will divide out and leave us with centimeters. 50 in. 2.54 cm 1 in. 50 in. 1 2.54 cm 1 in. Divide out the unit of inches. 127 cm 1 Multiply. 127 cm Simplify. Therefore, 50 in. 127 cm. Write out the example as you are reading it. YOU TRY 2 Convert to the indicated unit. Round the answer to the nearest tenth, if necessary. a) An art teacher mixes 3.5 c of water with some fl our to make plaster of Paris. Convert this number to milliliters. b) Anastasia is 152.4 cm tall. Convert this number to inches. c) A box contains 9 oz of fruit snacks. Convert this number to grams. www.mhhe.com/messersmith SECTION 7.5 Metric–U.S. Customary Conversions and Temperature 605
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