Units of Measurement - Trivium Test Prep Online Courses

# Units of Measurement

## Units of Measurement

The United States uses customary units, sometimes called standard units. In this system, several different units can be used to describe the same variable. These units and the relationships between them are shown in Table 3.6.

US Customary Units
Variable Measured
Unit
Conversions
Length
inches, foot, yard, mile
12 inches = 1 foot
3 feet = 1 yard
5280 feet = 1 mile
Weight
ounces, pound, ton
16 ounces = 1 pound
2000 pounds = 1 ton
Volume
fluid ounces, cup, pint, quart, gallon
8 fluid ounces = 1 cup
2 cups = 1 pint
2 pints = 1 quart
4 quarts = 1 gallon
Time
second, minute, hour, day
60 seconds = 1 minute
60 minutes = 1 hour
24 hours = 1 day
Area
square inch, square foot, square yard
144 square inches = 1 square foot
9 square feet = 1 square yard

Most other countries use the metric system, which has its own set of units for variables like length, weight, and volume. These units are modified by prefixes that make large and small numbers easier to handle. These units and prefixes are shown in Table 3.7.

Metric Units and Prefixes
Variable Measured
Base Unit
length
meter
weight
gram
volume
liter
Metric Prefix
Conversion
kilo
base unit × 1000
hecto
base unit × 100
deka
base unit × 10
deci
base unit × 0.1
centi
base unit × 0.01
milli
base unit × 0.001

Conversion factors are used to convert one unit to another (either within the same system or between different systems). A conversion factor is simply a fraction built from two equivalent values. For example, there are 12 inches in 1 foot, so the conversion factor is $$\frac{12\ in}{1\ ft}$$ or $$\frac{1\ ft}{12\ in}$$.

To convert from one unit to another, multiply the original value by a conversion factor. Choose a conversion factor that will eliminate the unwanted unit with the desired unit.

How many inches are in 6 feet?

$$6\ ft\ ×\ \frac{12\ in}{1\ ft} = \frac{6\ ft\ ×\ 12\ in}{1\ ft} = 72\ in$$

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