To find the unit rate of miles per gallon, you can use the formula:
\[ \text{Miles per gallon} = \frac{\text{Total miles driven}}{\text{Gallons of gas used}} \]
Lars can drive 330 miles on a full tank of gas, and the gas tank holds 15 gallons. Therefore, the calculation is:
\[ \text{Miles per gallon} = \frac{330 \text{ miles}}{15 \text{ gallons}} = 22 \text{ miles per gallon} \]
So, the unit rate is 22 miles per gallon.