A car travels 165 miles using 5.5 gallons of gas. What is the car's fuel efficiency in miles per gallon?

Miles per gallon is total miles divided by gallons used: 165 ÷ 5.5 = 30 mpg. Rate problems like this are solved by dividing the quantity (miles) by the unit you want it per (gallons). To divide by 5.5, you can multiply both numbers by 2 to clear the decimal: 330 ÷ 11 = 30. The car gets 30 miles per gallon. Keeping track of which quantity goes on top (the thing being measured, miles) and which on the bottom (the per-unit, gallons) is the key to setting up rate calculations correctly.