2013 AMC 10B Problem 8

Question

Ray’s car averages

40

miles per gallon of gasoline, and Tom’s car averages

10

miles per gallon of gasoline. Ray and Tom each drive the same number of miles. What is the cars’ combined rate of miles per gallon of gasoline?

10

16

25

30

40

Let both cars drive a convenient common distance

Combined miles per gallon is total miles divided by total gallons

Let each car drive

40

miles. Together they drive

80

miles.

Ray uses

1

gallon, while Tom uses

4

gallons, so together they use

5

gallons.

The combined rate is

80\div5=16

miles per gallon.

Thus, the correct answer is B .

Problem 8 in other years