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[Problem Solving]

试题详情

题目:

Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y. At these rates, if the two machines together produce 5/4 w widgets in 3 days, how many days would it take machine X alone to produce 2w widgets?

选项:

A、4
B、6
C、8
D、10
E、12

答案:

E

提问:

这题听过好几个录音,也知道效率是关键,我把X的效率表示为1/X,Y的效率表示为1/X-2,W就设为1,这样根据题干得出:[1/x+1/(x-2)]*3=5/4,可是解不出X 另外一种解法,我把W全都带入,最后W能消掉,可是扔解不出X,请老师指点

解答:

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