2021 AMC 10A Fall Problem 6

Below is the professionally curated solution for Problem 6 of the 2021 AMC 10A Fall, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2021 AMC 10A Fall solutions, or check the answer key.

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Concepts:ratio and proportionunit conversionfencepost counting

Difficulty rating: 870

6.

Elmer the emu takes 4444 equal strides to walk between consecutive telephone poles on a rural road. Oscar the ostrich can cover the same distance in 1212 equal leaps. The telephone poles are evenly spaced, and the 4141st pole along this road is exactly one mile (52805280 feet) from the first pole. How much longer, in feet, is Oscar's leap than Elmer's stride?

66

88

1010

1111

1515

Solution:

There are 4040 gaps between the 11 st and 4141 st pole, which means that the distance between consecutive poles is 5280÷40=132 5280 \div 40 = 132 feet.

This means that each of Elmer's strides is 132÷44=3 132 \div 44 = 3 feet. Similarly, each of Oscar's strides is 132÷12=11 132 \div 12 = 11 feet. This makes Oscar's leap 113=811 - 3 = 8 feet longer.

Thus, B is the correct answer.

Problem 6 in Other Years