John can mow a field in 6 hours. Bill can mow a field in 5 hours. Henry can mow a field in 4 hours. Joe can mow a field in 3 hou

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问题 John can mow a field in 6 hours. Bill can mow a field in 5 hours. Henry can mow a field in 4 hours. Joe can mow a field in 3 hours. Tom can mow a field in 2 hours. If they all work together at their respective rates, how long will it take to mow the field?

选项 A、41.4 minutes.
B、39.4 minutes.
C、40.4 minutes.
D、38.4 minutes.

答案A

解析 假设这块地的面积为1,可以求出他们单独割这块地时每小时割地的大小,继而可以得出如下的算式:
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