GWS一道题，答案总算不对，那位给解释一下

shaan

Company S produces two kinds of stereos:  basic and deluxe.  Of the stereos produced by Company S last month,  2/3were basic and the rest were deluxe.  If it takes  7/5 as many hours to produce a deluxe stereo as it does to produce a basic stereo, then the number of hours it took to produce the deluxe stereos last month was what fraction of the total number of hours it took to produce all the stereos?

这种题比较典型，但是发现GWD上面重复的答案总是7/17，那位给解答一下怎么算出来的，我怎么算都是5/19。

feifei531

我的想法是将全部设成共30个

那basic 就有20 个,并假设做一个需要1hr

则deluxe 就有10 个,题目给你做一个是basic的7/5就是需要7/5 hr

故(10*7/5)/(20*1+10*7/5)=7/17

zacharyzhang

由于是求比例，具体数量不影响比例，因此可以随便代。取方便计算的特殊值。

例如生产2B和1D，所用时间就是2t和7/5t，总时间是17/5t。

LZ的19怎么来的？2*7+5么？正确的应该是2*5+7=17才对么。

shaan

惭愧，单位搞混了