1971 AMC 12 第 2 题

Question

若

b

名工人用

c

天砌好

f

块砖，那么按相同速度，

c

名工人砌好

b

块砖所需的天数是：

If

b

men take

c

days to lay

f

bricks, then the number of days it will take

c

men working at the same rate to lay

b

bricks is:

fb^2

\frac{b}{f^2}

\frac{f^2}{b}

\frac{b^2}{f}

\frac{f}{b^2}

先求一名工人一天能砌多少块砖

Find the number of bricks laid by one man in one day

每个工日的效率是

\frac{f}{bc}

块砖

The rate is

\frac{f}{bc}

bricks per man-day

每个工日的效率是

\frac{f}{bc}

块砖。因此，

c

名工人每天砌

\frac{f}{b}

块砖，所以砌好

b

块砖需要

\frac{b}{\frac{f}{b}}=\frac{b^2}{f}

天。

因此，正确答案为 D。

The rate is

\frac{f}{bc}

bricks per man-day. Thus

c

men lay

\frac{f}{b}

bricks per day, so laying

b

bricks takes

\frac{b}{\frac{f}{b}}=\frac{b^2}{f}

days.

Therefore, the correct answer is D.

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