1.1 Units and Unit Conversion

Notes

A quantity is a number with a unit (meters, seconds, dollars). Always keep the unit with the number, and choose units that fit the situation.

• Length: mm, cm, m, km. Mass: g, kg. Time: s, min, h. Metric prefixes: kilo = 1000, centi = $\displaystyle \frac{1}{100}$, milli = $\displaystyle \frac{1}{1000}$.
• Area uses square units (like $\text{cm}^2$). Volume uses cubic units (like $\text{cm}^3$).
• To convert, multiply by a ratio equal to 1, such as $\displaystyle \frac{60 \text{ min}}{1 \text{ h}}$.
• Example: $2.5 \text{ h} = 2.5 \cdot 60 = 150 \text{ min}$.