2003 AMC 10B Problem 5

Below is the professionally curated solution for Problem 5 of the 2003 AMC 10B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2003 AMC 10B solutions, or check the answer key.

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Concepts:unit conversionratearea

Difficulty rating: 1100

5.

Moe uses a mower to cut his rectangular 9090-foot by 150150-foot lawn. The swath he cuts is 2828 inches wide, but he overlaps each cut by 44 inches to make sure that no grass is missed. He walks at the rate of 50005000 feet per hour while pushing the mower. Which of the following is closest to the number of hours it will take Moe to mow his lawn?

0.750.75

0.80.8

1.351.35

1.51.5

33

Solution:

The lawn has area 90150=13,50090 \cdot 150 = 13{,}500 square feet.

Each foot Moe walks mows an effective strip 22 feet wide, so he mows 25000=10,0002 \cdot 5000 = 10{,}000 square feet per hour. The time needed is 13,50010,000=1.35 hours.\dfrac{13{,}500}{10{,}000}=1.35 \text{ hours}.

Thus, the correct answer is C.

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