Prep DS 上的一道题， 答案错了吧

gelukkig

41.3690-!-item-!-187;#058&003497

Machines X and Y work at their respective constant rates.How many more hours does it take machine Y, working alone, to fill a production order of a certain size than it takes machine X, working alone?



(1) Machines X and Y, working together, fill a production order of this size in two-thirds the time that machine X, working alone, does.



(2) Machine Y, working alone, fills a production order of this size in twice the time that machine X, working alone, does.

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【答案】E

【思路】設work=1, machineX=Xhour, machineY=Yhour, 問y-x=?

(1)
--------------------------------------------------------------insufficient
(2)
-----------------------------------------------------------------------insufficient
(1)(2)------------------------------------------------------------------------------------insufficient

分明能求出来数值的好不好。X = 1, Y= 2, 应该选C 阿，    大家看看〉？

shirleylittl

没有错。（1）单独不可以 （2）单独也不可以 （1）和（2）算出的结果其实是一样的 y=2x，等价。没用的。
所以选E

gelukkig

我马虎了~~~谢谢回复