2010 AMC 12B 第 1 题

Question

Makayla 在

9

小时工作日中参加了两场会议。第一场会议用了

45

分钟，第二场会议用时是第一场的两倍。她工作日的百分之多少用于参加会议？

Makayla attended two meetings during her

9

-hour work day. The first meeting took

45

minutes and the second meeting took twice as long. What percent of her work day was spent attending meetings?

15

20

25

30

35

把工作日换算成分钟：

9

小时是

540

分钟

Convert the work day to minutes:

9

hours is

540

minutes

两场会议合计用时

45+2\cdot45

分钟

The two meetings together last

45+2\cdot45

minutes

两场会议用了

45+90=135

分钟，而工作日共有

9\cdot60=540

分钟。

用于开会的时间占全天的比例是

\frac{135}{540}=\frac14=25\%\text{。}

因此，正确答案是 C。

The two meetings lasted

45+90=135

minutes, and the work day is

9\cdot60=540

minutes.

The fraction of the day spent in meetings is

\frac{135}{540}=\frac14=25\%.

Thus, the correct answer is C.

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