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The Metric System
Functions
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3.7
Metric and U.S. Conversion
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3. Metric and U.S. Conversion
In technical work, you must sometimes change from one system of measurement to another. Most numbers are rounded to three or four significant digits. Due to this rounding and your choice of conversion factors, there may be a small difference in the last digit(s) of the answers involving conversion factors. This small difference is acceptable. In this section, round each result to three significant digits, when necessary.

4. Metric and U.S. Conversion
Figure 3.16 shows the relative sizes of each of four sets of common metric and U.S. units of area.
Relative sizes of some common metric and U.S. units of area
Figure 3.16

5. Example 1
Change 17 in. to centimetres.
conversion factor

6. Metric and U.S. Conversion
In the U.S. system, the acre is the basic unit of land area. Historically, the acre was the amount of ground that a yoke of oxen could plow in one day. 1 acre = 43,560 ft2 1 mi2 = 640 acres = 1 section

7. Metric and U.S. Conversion
Land areas in the United States are still typically measured in the U.S. system. When converting between metric and U.S. land-area units, use the following relationship: 1 hectare = 2.47 acres A good approximation is 1 hectare = 2.5 acres