Basic Mathematics for College Students

448 Chapter 5 Ratio, Proportion, and Measurement

Self Check 6

Convert 60 ounces to

pounds.

Now TryProblem 47

Self Check 7

Convert 60 pounds to

ounces.

Now TryProblem 51

EXAMPLE (^6) Convert 40 ounces to pounds.
StrategyWe will multiply 40 ounces by a carefully chosen unit conversion factor.
WHYIf we multiply by the proper unit conversion factor, we can eliminate the
unwanted units of ounces and convert to pounds.
Solution
To convert from ounces to pounds, we must chose a unit conversion factor whose
numerator contains the units we want to introduce (pounds), and whose
denominator contains the units we want to eliminate (ounces). Since there is
1 pound for every 16 ounces, we will use
To perform the conversion, we multiply.
Write 40 oz as a fraction: 40 oz . Then multiply by a
form of 1:
Multiply the fractions.
There are two ways to complete the solution. First, we can remove any common
factors of the numerator and denominator to simplify the fraction. Then we can
write the result as a mixed number.
A second approach is to divide the numerator by the denominator and express the
result as a decimal.
Perform the division: 40 16.
40 ounces is equal to 2 12 lb (or 2.5 lb).

40

16

lb2.5 lb

40

16

lb

5  8

1

2  8

1

lb

5

2

lb 2

1

2

lb



40

16

lb

Remove the common units of ounces from the numerator

 (^) and denominator. Notice that the units of pounds remain.
40 oz
1



1 lb

16 oz

1 lb

16 oz^.

40 oz

40 oz40 oz^1

1

#1 lb

16 oz

This is the unit we want to introduce.

 This is the unit we want to eliminate (the original unit).

1 lb

16 oz

EXAMPLE (^7) Convert 25 pounds to ounces.
StrategyWe will multiply 25 pounds by a carefully chosen unit conversion factor.
WHYIf we multiply by the proper unit conversion factor, we can eliminate the
unwanted units of pounds and convert to ounces.
Solution
To convert from pounds to ounces, we must chose a unit conversion factor whose
numerator contains the units we want to introduce (ounces), and whose
denominator contains the units we want to eliminate (pounds). Since there are
16 ounces per pound, we will use
This is the unit we want to introduce.
 This is the unit we want to eliminate (the original unit).
16 oz
1 lb
2.5
16 40.0
 32
80
 80
0