  ### Home > MC1 > Chapter 9 > Lesson 9.2.2 > Problem9-73

9-73.

Depending on the situation, numbers may be exact or approximate. Exact numbers are numbers from counting, mathematical relationships, definitions, or decisions. Approximate numbers arise from measurement or rounding.

Tell whether the number in each sentence is exact or approximate.

1. There are $12$ inches in a foot.

Are there exactly $12$ inches in a foot, or are there about $12$ inches in a foot?

Exact, since this is a mathematical relationship.

2. Sam's height is $157$ centimeters.

Do you think that Sam is exactly $157$ centimeters?
Is it possible that he is a few millimeters taller or shorter than this measurement?

Approximate, since this is a measurement.

3. There are four books on the shelf.

Did this number come from counting? If so, it is exact.

4. The driving age is $16$ years old.

The government decided that $16$ years old was the correct driving age.
Do you think this is an exact number or an approximate number?

5. It is $93{,}000{,}000$ miles from the earth to the sun.

Someone had to measure this distance.
Does that make it exact or approximate?

Approximate

6. With a tax rate of $8\%$, the tax on a $14.95$ CD is $1.20$.

Does this look approximate? You can do the work on your own to check if this number is exact.