Question

莫用割草机修剪一个 $90$ 英尺乘 $150$ 英尺的长方形草坪。割草机每次割出的宽度为 $28$ 英寸，但为了不漏草，他每次重叠 $4$ 英寸。他推割草机时的速度为每小时 $5000$ 英尺。下列哪个数最接近他割完整个草坪所需的小时数？

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?

$0.75$

$0.8$

$1.35$

$1.5$

$3$

答案：C

知识点：单位换算速率面积

难度评级：1100

小提示：

有效割草宽度为 $28-4=24$ 英寸，即 $2$ 英尺。

The effective swath width is $28-4=24$ inches, which is $2$ feet

大提示：

用草坪面积除以莫每小时割草面积。

Divide the lawn’s area by the area Moe mows per hour

解答：

草坪面积为 $90 \cdot 150 = 13{,}500$ 平方英尺。

莫每走一英尺，有效割草宽度为 $2$ 英尺，所以每小时割草面积为 $2 \cdot 5000 = 10{,}000$ 平方英尺。因此所需时间为 $\dfrac{13{,}500}{10{,}000}=1.35$ 小时。

所以正确答案是 C。

The lawn has area $90 \cdot 150 = 13{,}500$ square feet.

Each foot Moe walks mows an effective strip $2$ feet wide, so he mows $2 \cdot 5000 = 10{,}000$ square feet per hour. The time needed is $\dfrac{13{,}500}{10{,}000}=1.35$ hours.

Thus, the correct answer is C.

2003 AMC 10B 第 5 题

答案：C

难度评级：1100

小提示：

大提示：

解答：

其他年份的第 5 题