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 which of the following are exact numbers.

(a) the mass of a 32-oz can of coffee

(b) the number of students in your chemistry class

(c) the temperature of the surface of the Sun

(d) the mass of a postage stamp

(e) the number of milliliters in a cubic meter of water

(f) the average height of NBA basketball players

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