Section 9.4
Linear Measurement
The U.S. system of measurement uses the
inch, foot, yard, and mile to measure length.
U.S. Units of Length
Unit Fractions
12 inches (in.) = 1 foot (ft)
12 in.
1 ft
=
=1
1 ft
12 in.
3 ft 1 yd
=
=1
1 yd 3 ft
3 feet = 1 yard (yd)
5280 feet = 1 mile (mi)
5280 ft
1mi
=
=1
1mi
5280 ft
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To convert from one unit of length to
another, unit fractions may be used. A unit
fraction is a fraction that equals 1.
To convert 60 inches to feet, multiply by a unit
fraction that relates feet to inches. The unit fraction
should be written so that the units we are converting
to, feet, are in the numerator and the original units,
inches, are in the denominator.
Unit fraction
units converting to
60
in.
1
ft
60
 1 ft
60
ft
60 in. =

=
=
= 5 ft
1
12 in.
1  12
12
original units
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The basic unit of length in the metric
system is the meter. A meter is slightly
longer than a yard. It is approximately 39.37
inches long. Like the decimal system, the
metric system uses powers of ten to define
units.
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Metric System of Measurement
Prefix Meaning
Metric Unit of Length
kilo
1000
1 kilometer (km) = 1000 meters (m)
1 hectometer (hm) = 100 m
hecto
100
1 dekameter (dam) = 10 m
deka
10
1 meter (m) = 1 m
deci
1/10
1 decimeter (dm) = 1/10 or 0.1 m
centi
1/100
1 centimeter (cm) = 1/100 or 0.01 m
1 millimeter (mm) = 1/1000 or 0.001 m
milli
1/1000
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The most commonly used measurements of
length in the metric system are the meter,
millimeter, centimeter, and kilometer.
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As with the U.S. system of measurement,
unit fractions may be used to convert from
one unit of length to another. The major
advantage of the metric system is the ease
of converting from one unit of length to
another. Since all units of length are powers
of 10 of the meter, converting from one unit
of length to another is as simple as moving
the decimal point.
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Listing units of length in order from largest
to smallest helps keep track of how many
places to move the decimal point when
converting.
Start
km
hm
dam
m
End
dm
cm
mm
2 units to the right
Using the listing of units of length, convert
3.5 m to centimeters.
3.50 m = 350. cm or 350 cm
2 places to the right
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