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This module is from Fundamentals of Mathematics by Denny Burzynski and Wade Ellis, Jr. This module discusses the United States System of measurement. By the end of the module students should know what the word measurement means, be familiar with United States system of measurement and be able to convert from one unit of measure in the United States system to another unit of measure.

Section overview

  • Measurement
  • The United States System of Measurement
  • Conversions in the United States System

Measurement

There are two major systems of measurement in use today. They are the United States system and the metric system . Before we describe these systems, let's gain a clear understanding of the concept of measurement.

Measurement

Measurement is comparison to some standard.

Standard unit of measure

The concept of measurement is based on the idea of direct comparison. This means that measurement is the result of the comparison of two quantities. The quantity that is used for comparison is called the standard unit of measure .

Over the years, standards have changed. Quite some time in the past, the stan­dard unit of measure was determined by a king. For example,
1 inch was the distance between the tip of the thumb and the knuckle of the king.
1 inch was also the length of 16 barley grains placed end to end.

Today, standard units of measure rarely change. Standard units of measure are the responsibility of the Bureau of Standards in Washington D.C.

Some desirable properties of a standard are the following:

  1. Accessibility . We should have access to the standard so we can make comparisons.
  2. Invariance . We should be confident that the standard is not subject to change.
  3. Reproducibility . We should be able to reproduce the standard so that measure­ments are convenient and accessible to many people.

The united states system of measurement

Some of the common units (along with their abbreviations) for the United States system of measurement are listed in the following table.

Unit Conversion Table
Length 1 foot (ft) = 12 inches (in.)
1 yard (yd) = 3 feet (ft)
1 mile (mi) = 5,280 feet
Weight 1 pound (lb) =16 ounces (oz)
1 ton (T) = 2,000 pounds
Liquid Volume 1 tablespoon (tbsp) = 3 teaspoons (tsp)
1 fluid ounce (fl oz) = 2 tablespoons
1 cup (c) = 8 fluid ounces
1 pint (pt) = 2 cups
1 quart (qt) = 2 pints
1 gallon (gal) = 4 quarts
Time 1 minute (min) = 60 seconds (sec)
1 hour ( hr) = 60 minutes
1 day (da) = 24 hours
1 week (wk) = 7 days

Conversions in the united states system

It is often convenient or necessary to convert from one unit of measure to another. For example, it may be convenient to convert a measurement of length that is given in feet to one that is given in inches. Such conversions can be made using unit fractions .

Unit fraction

A unit fraction is a fraction with a value of 1.

Unit fractions are formed by using two equal measurements. One measurement is placed in the numerator of the fraction, and the other in the denominator. Place­ment depends on the desired conversion .

Placement of units

Place the unit being converted to in the numerator .
Place the unit being converted from in the denominator .

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Source:  OpenStax, Contemporary math applications. OpenStax CNX. Dec 15, 2014 Download for free at http://legacy.cnx.org/content/col11559/1.6
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