1950 AMC 12 Problem 27

Attempt Problem 27 of the 1950 AMC 12 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1950 AMC 12 solutions, or check the answer key.

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27.

A car travels 120120 miles from AA to BB at 3030 miles per hour but returns the same distance at 4040 miles per hour. The average speed for the round trip is closest to:

3333 mph

3434 mph

3535 mph

3636 mph

3737 mph

Answer: B
Concepts:distance rate and timeestimation
Difficulty rating: 1410
Small Hint:

Average speed is total distance divided by total time

Big Hint:

The two legs take 12030\frac{120}{30} and 12040\frac{120}{40} hours

Solution:

The total distance is 240240 miles. The travel times are 44 hours and 33 hours, so the average speed, in miles per hour, is 2404+3=240734.29 \frac{240}{4+3}=\frac{240}{7}\approx34.29 which is closest to 3434 mph.

Thus, the correct answer is B.

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Full Exam

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