### 1.4 Units & Conversions

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• Math Help

Although most countries use the metric system, Americans have resisted switching from the customary system to metric. Perhaps one reason is that the customary system evolved naturally in accord with the human body. The metric system is patterned after "base 10" and the circumference of Earth. Here are some examples.

• Inch
• Foot
• Yard
• Mile

#### Historical Beginning

• The width of a human thumb.
• The length of a human foot.
• The distance from a human nose to the end of an outstretched human arm.
• The distance a human can walk in 1000 paces (two steps).

Pounds, ounces, quarts, gallons, and other measures in the U.S. customary system have similar connections to humans and human activities, such as measuring food, precious metals, and grain.

• Consumer Suggestion

The calendar used in the United States and the one that you are most familiar with is referred to as the Gregorian calendar. This calendar's original purpose was to regulate ceremonial cycles of the Roman Catholic and Protestant churches. Find more information about the origins of this calendar by clicking here.

• Checkpoint Solution

From Example 3, you know that there are

31,536,000 seconds

in a calendar year. Because there are 365.24218967 days in a solar year, there are

in a solar year.

So, there are about 20,925 more seconds in a solar year than in a calendar year.

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``` __   _    __   __    _  __    _____    _    _
| || | ||  \ \\/ //  | |/ //  |  ___|| | |  | ||
| '--' ||   \ ` //   | ' //   | ||__   | |/\| ||
| .--. ||    | ||    | . \\   | ||__   |  /\  ||
|_|| |_||    |_||    |_|\_\\  |_____|| |_// \_||
`-`  `-`     `-`'    `-` --`  `-----`  `-`   `-`

```