AMC10 2003 B

AMC10 2003 B · Q5

AMC10 2003 B · Q5. It mainly tests Rates (speed), Rounding & estimation.

Moe uses a mower to cut his rectangular 90-foot by 150-foot lawn. The swath he cuts is 28 inches wide, but he overlaps each cut by 4 inches to make sure that no grass is missed. He walks at the rate of 5000 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?

Moe 用割草机修剪他的 90 英尺乘 150 英尺的矩形草坪。割草宽度为 28 英寸，但他每条割草重叠 4 英寸以确保不漏草。他推着割草机行走速度为每小时 5000 英尺。Moe 修剪草坪需要多长时间（小时）？以下哪个最接近？

(A) 0.75 0.75

(B) 0.8 0.8

(D) 1.5 1.5

(E) 3 3

Answer

Correct choice: (C)

正确答案：（C）

Solution

The area of the lawn is $90 \cdot 150 = 13,500$ ft$^2$. Moe cuts about two square feet for each foot he pushes the mower forward, so he cuts $2(5000) = 10,000$ ft$^2$ per hour. Therefore, it takes about $13,500 / 10,000 = 1.35$ hours.

草坪面积为 $90 \cdot 150 = 13,500$ ft$^2$。Moe 每推进一步割大约两平方英尺，所以每小时割 $2(5000) = 10,000$ ft$^2$。因此，需要约 $13,500 / 10,000 = 1.35$ 小时。

Topics