5.3 American Units of Measurement 443SECTION 5.3
American Units of Measurement
Objectives
1 Use a ruler to measure lengths
in inches.
2 Define American units of
length.
3 Convert from one American
unit of length to another.
4 Define American units of
weight.
5 Convert from one American
unit of weight to another.
6 Define American units of
capacity.
7 Convert from one American
unit of capacity to another.
8 Define units of time.9 Convert from one unit of time
to another.Two common systems of measurement are the American(or English) system and the
metric system.We will discuss American units of measurement in this section and
metric units in the next. Some common American units are inches, feet, miles, ounces,
pounds, tons, cups, pints, quarts,and gallons.These units are used when measuring
length, weight, and capacity.
Use a ruler to measure lengths in inches.
A ruler is one of the most common tools used for measuring distances or lengths. The
figure below shows part of a ruler. Most rulers are 12 inches (1 foot) long. Since
12 inches 1 foot, a ruler is divided into 12 equal lengths of 1 inch. Each inch is
divided into halves of an inch, quarters of an inch, eighths of an inch, and sixteenths
of an inch.
The left end of a ruler can be (but sometimes isn’t) labeled with a 0. Each point on
a ruler, like each point on a number line, has a number associated with it.That number
is the distance between the point and 0. Several lengths on the ruler are shown below.
0 1 2
Inches3
(^1) –
2
2 in.
(^1) –
4
3 in.
(^7) –
18 in.
1 in.
Actual size
1
Milk is sold
in gallon
containers.
First-class postage for a
letter that weighs less
than 1 ounce is 44¢.
A newborn baby is
20 inches long.
POSTAGESTAMPUS
One Gallon
Whole
Vitamin A & D Milk
added
EXAMPLE (^1) Find the length of the paper clip
shown here.
StrategyWe will place a ruler below the paper clip,
with the left end of the ruler (which could be thought of
as 0) directly underneath one end of the paper clip.
WHYThen we can find the length of the paper clip by identifying where its other
end lines up on the tick marks printed in black on the ruler.