2014 AMC 10B 第 8 题

Question

一辆卡车每

t

秒行驶

\dfrac{b}{6}

英尺。

3

英尺等于一码。这辆卡车在

3

分钟内行驶多少码？

A truck travels

\dfrac{b}{6}

feet every

t

seconds. There are

3

feet in a yard. How many yards does the truck travel in

3

minutes?

\dfrac{b}{1080t}

\dfrac{30t}{b}

\dfrac{30b}{t}

\dfrac{10t}{b}

\dfrac{10b}{t}

先把英尺换成码，再按时间放大。

Convert feet to yards before scaling the time

三分钟是

180

秒。

Three minutes is

180

seconds

卡车每

t

秒行驶

\dfrac{b}{18}

码，因为

3

英尺等于一码；所以卡车每秒行驶

\dfrac{b}{18t}

码。

3

分钟为

180

秒，因此行驶

\dfrac{b}{18t}\cdot 180 = \dfrac {10b}t\text{。}

所以正确答案是 E。

This means it travels

\dfrac{b}{18}

yards in

t

seconds since a yard is

3

feet. Then, in one second, it travels

\dfrac{b}{18t}

yards.

Therefore, in

3

minutes which is

180

seconds, it travels

\dfrac{b}{18t}\cdot 180 = \dfrac {10b}t.

Thus, the correct answer is E .

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