Basic Mathematics for College Students

472 Chapter 5 Ratio, Proportion, and Measurement

Self Check 3

Convert 68 pounds to

grams. Round to the

nearest gram.

Now TryProblem 21

Self Check 4

BODY WEIGHT Who weighs

more, a person who weighs

165 pounds or one who weighs

76 kilograms?

Now TryProblem 25

EXAMPLE (^3) Convert 50 pounds to grams.
StrategyWe will use a two-part multiplication process that converts 50 pounds to
ounces, and then converts that result to grams.
WHYWe must use a two-part process because the conversion table on page 471
does not contain a single unit conversion factor that converts from pounds to grams.
Solution
Since there are 16 ounces per pound, we can convert 50 pounds to ounces
by multiplying by the unit conversion factor. Since there are approximately
28.35 g per ounce, we can convert that result to grams by multiplying by the unit
conversion factor.
Write 50 lb as a fraction:. Multiply
by two forms of 1: and.
Simplify.
Multiply: 50  16 800.
Do the multiplication.
Thus, 50 pounds 22,680 grams.
22,680 g
 800 28.35 g
 50  16 28.35 g
Remove the common units of pounds and ounces
from the numerator and denominator. The units
of grams remain.



50 lb

1



16 oz

1 lb



28.35 g

1oz

28.35 g

1 oz^

16 oz

1 lb

50 lb50 lb 1

50 lb

50 lb

1



16 oz

1 lb



28.35 g

1 oz

28.35 g

1 oz^

16 oz

1 lb^

2

6

8

2

.3

4

5

 800

22680.00

1

3

6

 50

800

EXAMPLE (^4) Packaging Does a 2.5 pound tub of butter weigh more
than a 1.5-kilogram tub?
StrategyWe will convert the weight of the 1.5-kilogram tub of butter to pounds.
WHYThen we can compare the weights of the tubs of butter in the same units,
pounds.
Solution
To convert 1.5 kilograms to pounds we must choose a unit conversion factor whose
numerator contains the units we want to introduce (pounds), and whose
denominator contains the units we want to eliminate (kilograms). From the second
row of the Metric to American column of the table, we see that there are
approximately 2.20 pounds per kilogram. Thus, we will use the unit conversion
factor:
To perform the conversion, we multiply.
Write 1.5 kg as a fraction:.
Multiply by a form of 1:.
Simplify.
Do the multiplication.
Since a 1.5-kilogram tub of butter weighs about 3.3 pounds, the 1.5-kilogram tub
weighs more.
3.3 lb
1.52.20 lb
Remove the common units of kilograms from
the numerator and denominator. The units
of pounds remain.



1.5 kg

1



2.20 lb

1 kg

2.20 lb

1 kg^

1.5 kg1.5 kg 1.5 kg1.5 kg^1

1



2.20 lb

1 kg

This is the unit we want to introduce.

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

2.20 lb

1 kg

2.20

1.5

1100

2200

3.300