**Definition: **Direct proportion is the relationship between two variables when their ratio is equal to a constant value.

## Examples:

- The volume of an ideal gas is directly proportional to the absolute temperature of the gas (Charles' Law)
- If you get paid by the hour, the more you work the more you will get paid. If you earn $15/hour and work 2 hours, you will earn $30 (Not including taxes, etc.) and if you work 4 hours, you will earn $60. The ratio of money earned to hours worked is 15 to 1 or $15/hour.