prep上的一道数学题！麻烦大家了！O(∩_∩)O谢谢！

芽儿zhao · 发表于 2011-7-29 16:59:20

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.

答案是E。我怎么觉得是C呢？麻烦NN分析一下！谢谢谢谢！

katrinali1990 · 发表于 2011-7-29 17:48:45

两个方程得出来的结果都是X=2Y 没有唯一解呀~~你化简后看

cicy11 · 发表于 2011-7-29 18:25:12

你只能得出的是x的工作效率是y的二倍。但是确切的时间没法知道。
题目中是How many hours这个是个确切的时间。但是两个都木法得出来。

prep上的一道数学题！麻烦大家了！O(∩_∩)O谢谢！

所属分类: GMAT考试

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