1950 AMC 12 Problem 28

Attempt Problem 28 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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28.

Two boys AA and BB start at the same time to ride from Port Jervis to Poughkeepsie, 6060 miles away. AA travels 44 miles an hour slower than B.B. BB reaches Poughkeepsie and at once turns back meeting AA 1212 miles from Poughkeepsie. The rate of AA was:

44 mph

88 mph

1212 mph

1616 mph

2020 mph

Answer: B
Concepts:distance rate and timerelative speedratio and proportion
Difficulty rating: 1640
Small Hint:

By the meeting time, AA has traveled 4848 miles

Big Hint:

In the same time, BB has traveled 60+12=7260+12=72 miles

Solution:

At the meeting point, AA has traveled 6012=4860-12=48 miles and BB has traveled 60+12=7260+12=72 miles. Since their travel times are equal, their speeds are in the ratio 48:72=2:3.48:72=2:3. If AA’s speed is v,v, then BB’s is v+4,v+4, so vv+4=23. \frac{v}{v+4}=\frac23. Thus 3v=2v+8,3v=2v+8, and v=8v=8 mph.

Thus, the correct answer is B.

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