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[Problem Solving]
试题详情
题目：
Three printing presses, R , S , and T , working together at their respective constant rates, can do a certain printing job in 4 hours. S and T , working together at their respective constant rates, can do the same job in 5 hours. How many hours would it take R , working alone at its constant rate, to do the same job?
选项:
A、8
B、10
C、12
D、15
E、20
答案:
E
提问：
may老师 请问这道题该怎么做 这种效率问题从小学就搞不明白
解答：
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提问：
may老师 请问这道题该怎么做 这种效率问题从小学就搞不明白
解答：
点赞0
阅读843
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