Practice problems for these concepts can be found at:
Measurement Practice Problems: GED Math
Types of Measurements
Units tell us two important things about the object being measured—what is being measured and its size. Are you measuring capacity, weight, length, or temperature? And how big, heavy, long, or hot is the object? For each type of measurement, you must use an appropriate unit of measurement. For example, you might use grams to measure weight, liters to measure capacity, degrees to measure temperature, feet to measure height, and so on.
Today, there are two major systems of measurement. The U.S. customary system is used in everyday life in the United States. The following are the types of measurements used most frequently in the United States:
Units of Length
1 foot (ft.) = 12 inches (in.)
1 yard (yd.) = 3 feet = 36 inches
1 mile (mi.) = 1,760 yards = 5,280 feet
1 square foot (ft.^{2}) = 144 square inches (in.^{2})
1 square yard (yd.^{2}) = 9 square feet
1 square mile (mi.^{2}) = 640 acres = 3,097,600 square yards
1 acre (A) = 4,840 square yards = 43,560 square feet
1 cubic foot (ft.^{3}) = 1,728 cubic inches (in.^{3}) ≈* 7.48 gallons
1 cubic yard (yd.^{3}) = 27 cubic feet
Units of Volume
1 tablespoon (tbs.) = 0.5 fluid ounce (fl. oz.)**
1 tablespoon = 3 teaspoons (tsp.)
1 cup (c.) = 8 fluid ounces
1 pint (pt.) = 2 cups = 16 fluid ounces
1 quart (qt.) = 2 pints = 32 fluid ounces
1 gallon (gal.) = 4 quarts = 128 fluid ounces
1 gallon ≈* 231 cubic inches ≈* 0.1337 cubic foot
Units of Weight
1 pound (lb.) = 16 ounces (oz.)**
1 ton (T) = 2,000 pounds
Units of Time
1 minute (min.) = 60 seconds (sec.)
1 hour (hr.) = 60 minutes
1 day = 24 hours
1 week = 7 days
1 year (yr.) = 52 weeks
1 year = 12 months
1 year = 365 days
*The symbol ≈means about equal to.
**Notice that ounces are used to measure the dimensions of both volume and weight.
The other major system of measurement is the metric system. This system is used in most other industrialized countries outside of the United States. It is also used by doctors and scientists in the United States. The basic units of the metric system are the meter, gram, and liter.
Converting units in the metric system is much easier than converting units in the U.S. customary system of measurement. However, making conversions between the two systems is much more difficult. Luckily, the GED test will provide you with the appropriate conversion factor when needed. Here is a general idea of how the two systems compare:
Conversions between U.S. Customary and Metric Units
1 inch ≈25.4 millimeters ≈2.54 centimeters
1 foot ≈0.3048 meter ≈30.480 centimeters
1 yard ≈0.9144 meter
1 mile ≈1,609.34 meters ≈1.6093 kilometers
1 kilometer ≈0.6214 mile
1 meter ≈3.281 feet ≈39.37 inches
1 square inch ≈ 645.16 square millimeters ≈ 6.4516 square centimeters
1 square foot ≈0.0929 square meter
1 square yard ≈0.8361 square meter
1 square mile ≈2,590,000 square meters ≈2.59 square kilometers
1 acre ≈4,046.8564 square meters ≈0.004047 square kilometer
1 cubic inch ≈16,387.064 cubic millimeters ≈16.3871 cubic centimeters
1 cubic foot ≈0.0283 cubic meter
1 cubic yard ≈0.7646 cubic meter
1 teaspoon ≈5 milliliters
1 tablespoon ≈15 milliliters
1 fluid ounce ≈29.57 milliliters ≈2.957 centiliters
1 fluid ounce ≈0.00002957 cubic meter
1 gallon ≈3.785 liters
1 liter ≈1.057 quarts ≈0.264 gallon
1 quart ≈0.946 liter
Prefixes are attached to the basic metric units to indicate the amount of each unit.
For example, the prefix deci means onetenth ; therefore, one decigram is onetenth of a gram, and one decimeter is onetenth of a meter. The following six prefixes can be used with every metric unit:
1 hectometer = 1 hm = 100 meters
1 millimeter = 1 mm = meter = .001 meter
1 dekagram = 1 dkg = 10 grams
1 centiliter = 1 cL* = liter = 0.01 liter
1 kilogram = 1 kg = 1,000 grams
1 deciliter = 1 dL* = liter = 0.1 liter
*Notice that liter is abbreviated with a capital letter—L.
The following are some common relationships used in the metric system:
Units of Length
1 centimeter (cm) = 10 millimeters (mm)
1 meter (m) = 100 centimeters = 1,000 millimeters
1 kilometer (km) = 1,000 meters
1 square centimeter (cm^{2}) = 100 square millimeters(mm2)
1 square meter (m^{2}) = 10,000 square centimeters = 1,000,000 square millimeters
1 square kilometer (km^{2}) = 1,000,000 square meters
1 cubic centimeter (cm^{3}) = 1,000 cubic millimeters (mm^{3})
1 cubic meter (m^{3}) = 1,000,000 cubic centimeters

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