Basic Mathematics for College Students

Chapter 5 Summary and Review 485

SECTION 5.3 American Units of Measurement

The American system of measurementuses the

units ofinch, foot, yard,and mileto measure

length.

A ruleris one of the most common tools for

measuring lengths. Most rulers are 12 inches

long. Each inch is divided into halves of an

inch, quarters of an inch, eighths of an inch, and

sixteenths of an inch.

DEFINITIONS AND CONCEPTS EXAMPLES

1 ft = 12 in. 1 yd = 3 ft

1 yd = 36 in. 1 mi = 5,280 ft

Since the black tick marks between 0 and 1 on the ruler create sixteen

equal spaces, the ruler is scaled in sixteenths.

––^3

16 in.

1 2 3

(^1) –
2 in.
(^1) –
14 in.
(^3) –
14 in.
(^3) –
28 in.
16 spaces
To convert from one unit of length to another,
we use unit conversion factors.They are called
unit conversion factors because their value is 1.
Multiplying a measurement by a unit
conversion factor does not change the measure;
it only changes the units of the measure.
A list of unit conversion factors for American
units of length is given on page 445.
Convert 4 yards to inches.
To convert from yards to inches, we select a unit conversion factor that
introduces the units of inches and eliminates the units of yards. Since
there are 36 inches per yard, we will use:
To perform the conversion, we multiply.
Write 4 yd as a fraction.
Then multiply by a form of 1:.
Simplify.
Do the multiplication.
Thus, 4 yards = 144 inches.
144 in.
 4 36 in.
Remove the common units of yards from
the numerator and denominator. The
units of inches remain.



4 yd

1



36 in.

1 yd

36 in.

1 yd^

4 yd

4 yd

1



36 in.

1 yd

This is the unit we want to introduce.

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

36 in.

1 yd

The American system of measurement uses the

units ofounce, pound, and tonto measure

weight.

1 lb = 16 oz 1 ton = 2,000 lb

A list of unit conversion factors for American

units of weight is given on page 447.

Convert 9,000 pounds to tons.

To convert from pounds to tons, we select a unit conversion factor that

introduces the units of tons and eliminates the units of pounds. Since

there is 1 ton for every 2,000 pounds, we will use:

This is the unit we want to introduce.

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

1 ton 

2,000 lb