Basic Mathematics for College Students

Define units of time.

The American system of measurement (and the metric system) use the units of

second, minute, hour,anddayto measure time. These units are related as follows.

Units of Time

1 minute (min)60 seconds (sec) 1 hour (hr)60 minutes

1 day24 hours

The abbreviation for each unit is written within parentheses.

To convert units of time, we use the following unit conversion factors. Each

conversion factor shown below is a form of 1.

8

450 Chapter 5 Ratio, Proportion, and Measurement

EXAMPLE (^8) Cooking If a recipe calls for 3 pints of milk, how many
fluid ounces of milk should be used?
StrategyWe will use a two-part multiplication process that converts 3 pints to
cups and then converts that result to fluid ounces.
WHYWe must use a two-part process because the table on page 449 does not
contain a single unit conversion factor that converts from pints to fluid ounces.
Solution
Since there are 2 cups per pint, we can convert 3 pints to cups by multiplying by the
unit conversion factor. Since there are 8 fluid ounces per cup, we can convert
that result to fluid ounces by multiplying by the unit conversion factor.
Write 3 pt as a fraction:.
Multiply by two unit conversion factors:
and.
Simplify.
Multiply.
Since 3 pints is equal to 48 fluid ounces, 48 fluid ounces of milk should be used.
 48 fl oz
 3 # 2 #8 fl oz
Remove the common units of pints and cups in
the numerator and denominator. Notice that all
the units are removed except for fluid ounces.



3 pt

1



2 c

1 pt



8 fl oz

1 c

8 fl oz

1 c ^1

2 c

1 pt^1

3 pt  3 pt 1

3 pt

3 pt

1

#2 c

1 pt

#8 fl oz

1 c

8 fl oz

1 c

2 c

1 pt^

Self Check 8

Convert 2.5 pints to fluid

ounces.

Now TryProblem 55

© Felix Wirth/Corbis

Use the unit Use the unit

To convert conversion To convert conversion

from factor from factor

minutes to seconds seconds to minutes

hours to minutes minutes to hours

days to hours 24 hr1 day hours to days 1 day24 hr

1 hr

60 min

60 min

1 hr

1 min

60 sec

60 sec

1 min