Question

A college student drove his compact car $120$ miles home for the weekend and averaged $30$ miles per gallon. On the return trip the student drove his parents' SUV and averaged only $20$ miles per gallon. What was the average gas mileage, in miles per gallon, for the round trip?

$22$

$24$

$25$

$26$

$28$

Answer: B

Concepts:distance rate and time harmonic mean

Difficulty rating: 990

Solution:

The trip home uses $120/30=4$ gallons, and the return trip uses $120/20=6$ gallons.

The round trip covers $240$ miles on $10$ gallons, so the average is $\dfrac{240}{10}=24.$

Thus, the correct answer is B.

2007 AMC 12B Problem 2

Answer: B

Difficulty rating: 990

Solution:

Problem 2 in Other Years