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:
- Accessibility . We should have access to the standard so we can make comparisons.
- Invariance . We should be confident that the standard is not subject to change.
- 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 .