Recall that **Exact numbers are either defined numbers or the result of a count**.

- Examples of exact numbers are the following:
**Conversions within the American system**(such as pounds to ounces, the number of feet in a mile, the number of inches in a foot, etc).**Conversions with the metric system**(such as kilograms to grams, the number of meters in a kilometer, the number of centimeters in a meter).**The words**, respectively.*per*and*percent*mean exactly out of one or one hundred**Counted numbers are exact**: there are two chairs in the photograph. There are fifteen books on the shelf. Eighty-seven people attended the lecture.

An exact number can only be expressed in one way and cannot be simplified any further. E**xact numbers have an infinite number of significant figures, but they often appear as integers**.

Indicate whether each of the following can be determined exactly or must be measured with some degree of uncertainty:

(c) the number of gallons of gasoline necessary to fill an automobile gas tank

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Our data indicates that this problem or a close variation was asked in Chemistry - OpenStax 2015th Edition. You can also practice Chemistry - OpenStax 2015th Edition practice problems.