Preparing to DLR-Math

Question

Here is a question which I could not solve when preparing for my exam.

A car averages 27 miles per gallon. If gas costs $4.04 per gallon, which of the following is closest to how much gas would cost for this car to travel 2,727 typical miles?

My closest answer: $109.08

Answer 1

Use the units to guide your arithmetic. You are given:

• The mileage of the car, in miles per gallon.
• The price of gasoline, in dollars per gallon.
• The distance to travel, in miles.

You want to know the cost of the journey, in dollars. Essentially, you want to convert that quantity of miles into a dollar amount.

When multiplying units, you can cancel units that appear in the numerator and denominator. Like so: $$ \require{cancel} (2727\,\cancel{\text{miles}}) \left(\frac{1\,\cancel{\text{gallon}}}{27\,\cancel{\text{miles}}}\right) \left(\frac{\$4.04}{1\,\cancel{\text{gallon}}}\right) = \$408.04 $$