How to Convert Units in the English System of Measurement Video

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  • 0:04 Converting Units of…
  • 0:56 Conversion Factors
  • 1:33 Converting From One…
  • 4:52 Lesson Summary
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Lesson Transcript
Instructor: Russell Frith
In this lesson, we will learn how to convert one unit of measurement in the English measurement system, as measured in distance, area, and volume, to another unit of measurement.

Converting Units of English Measure

Have you ever wanted to know how many inches are in a mile? How many square feet are in an acre? How many cubic feet are in a cubic yard? At first, these questions seem somewhat odd but the answers are very important. For instance, the question 'how many cubic feet are in a cubic yard?' must be answered by construction workers when they pour concrete for a building foundation. The answer to the question 'how many square feet are in an acre?' needs to be answered by real estate surveyors when they partition a tract of land for a high-density housing project.

In this lesson, we will learn how to convert one unit of measurement in the English measure system to another. The conversion method is not as straightforward as the metric system. The unusual conversion methods date back several hundred years when English surveyors and navigators were trying to develop standard units for measuring distance, area, and volumes.

Conversion Factors

When converting from one unit of measure to another, you should know what is called a conversion factor. Examples of conversion factors would be:

  • 36 inches equals one yard
  • 5,280 feet equals one mile

In English measurements, the acre is a unit of measurement for an enclosed, two-dimensional area. Think of an acre as a square that is 43,560 square feet = 4,840 square yards = 1/640 square mile. Of course, we can measure area in terms of square inches, square feet, or square miles.

Converting From One Unit to Another

To convert from one unit of measure to another, we use the method of unit analysis. Here are some examples of how this method works.

First, how many inches are in 17 feet?

We know that 12 inches equal 1 foot, so we multiply:

17 feet * 12 inches/foot = 204 inches.

In this solution, the foot measurements canceled out in the multiplication, leaving only inches. Notice that the multiplier on 17 feet, 12 inches/foot, is an identity in the multiplication; that is, 12 inches/foot equals 1.

Let's look at another example.

How many miles are in 25,000 yards?

From the table, we know that one mile is 1,760 yards. Using unit analysis, we get:

25,000 yards * 1 mile/1,760 yards = 14.2045 miles.

Here's another example.

How many square feet are in 100 acres?

There are 43,560 square feet in an acre. Thus, 100 acres in square feet are:

100 acres x 43,560 square feet/1 acre = 4,356,000 square feet.

Next, let's answer this question:

How many square feet are in 1,440 square inches?

We know that 1 foot equals 12 inches. Thus, squaring both sides gives us one square foot equaling 144 square inches. Subsequently, we get:

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