## What Do the Numbers Mean?

## Opening

# What Do the Numbers Mean?

You can get a new unit by dividing two other units. In fact, that is what defines a rate. For instance, if you divide 10 meters by 2 seconds, you get 5 $\frac{\text{meters}}{\mathrm{second}}$. The new unit is “meters per second.”

When multiplying and dividing units, you can cancel them out as shown here.

$\begin{array}{c}\text{inches}\xb7\text{}\frac{\text{centimeters}}{\text{inches}}=\text{centimeters}\\ 12\text{in}\text{.}\xb7\text{2}\text{.54}\frac{\text{cm}}{\text{in}\text{.}}=\text{30}\text{.48 cm}\end{array}$

- Discuss with your partner why units cancel out.
- What would be the correct unit for this equation?

30.48 cm • 0.3937$\frac{\text{in}}{\text{cm}}$ = 12 ___