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PREP5的IR题目

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发表于 2021-8-26 10:45:13 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
Perry, Maria, and Lorna are painting rooms in a college dormitory. Working alone, Perry can paint a standard room in 3 hours, Maria can paint a standard room in 2 hours, and Lorna can paint a standard room in 2 hours 30 minutes. Perry, Maria, and Lorna have decided that, to speed up the work, 2 of them will paint a standard room together.
Select the value closest to the shortest time in which a 2-person team could paint a standard room, and select the value closest to the longest time in which a 2-person team could paint a standard room, with each person working at his or her respective rate. Make only two selections, one in each column.
Shortest time
Longest time
49 minutes
1 hour 7 minutes
1 hour 12 minutes
1 hour 14 minutes
1 hour 22 minutes
1 hour 45 minutes
请问一下这题怎么做呀,我把每个人的效率都求出来,然后用1除以效率的相加得出时间,可是没答案呀,是我理解错了吗
谢谢大家!
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