2 Use Multiplication or Division to Convert Between Units How do we know whether we multiply or divide to change units? Use these guidelines. Procedure Use Multiplication or Division to Convert Between Units 1) When converting from a larger unit to a smaller unit, use multiplication. 2) When converting from a smaller unit to a larger unit, use division. Convert each measurement to the indicated unit. a) 4 ft to inches b) 1.5 days to hours c) 2 1 2 c to pints Solution a) First, we need to know that 1 ft 12 in. Next, notice that we are changing from a larger unit, feet, to a smaller unit, inches. So to change 4 ft to inches, we multiply. 4 12 48 in. 12 in. 1 ft Therefore, 4 ft 48 in. b) Since we are asked to convert 1.5 days to hours, we need to know that 1 day 24 hr. We are changing from a larger unit, days, to a smaller unit, hours. To change 1.5 days to hours, we will multiply. 1.5 24 36 24 hr 1 day So, 1.5 days 36 hr. c) First ask yourself, “How are cups and pints related?” 2 c 1 pt. This time we are asked to convert from a smaller unit, cups, to a larger unit, pints. Therefore, we will divide. Change 2 1 2 to 5 2 . 2 1 2 2 5 2 2 1 5 2 1 2 5 4 1 1 4 or 1.25 Write 2 as 2 1 . Change division to multiplication by the reciprocal. Therefore, 2 1 2 c 1 1 4 pt or 1.25 pt. Look at the relationships between measurements in Objective 1. What do you notice that helps this make sense? EXAMPLE 2 Note If we get an improper fraction for a unit of measurement, we usually write it as a mixed number or as a decimal. 568 CHAPTER 7 Measurement and Conversion www.mhhe.com/messersmith
messersmith_power_prealgebra_1e_ch4_7_10
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