另一道prep DS

安静的小兔 · 发表于 2010-10-5 12:26:09

Are at least 10 percent of the people in country X who are 65 yrs old or older employed?
1) in country X, 11.3 percent of population is 65 yrs old or older
2)in country X, of the population 65 yrs old or older , 20 percent of the men and 10 percent of the women are employed

Source: Gmatprep 1 ...DS

ANS:-B
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mahattangmat解释：

Statement 1 - gives percent of people in the age group, but there is no mention of employment figures. Not sufficient

Statement 2 - it gives the percent of men (20%) and women (10%) over 65 years AND who are employed. The total number of men and women in this age group is not given. let us assume it is denoted by M and W. hence the total figure is

( 20 % of M + 10 % of W )
------------------------------
( M + W )

this gives a weighted average whose value will always be greater than 10 and less than 20.

So infact M and W is not required to answer teh solution.

还是不太明白啊~

快乐小龙 · 发表于 2010-10-5 12:32:17

集合四个元素
男+女=总人数
+65有工作=20%的男人+10%的女人
那么加权平均后的结果肯定在10-20之间的，就是肯定大于10%了

这道题目比较狡猾

安静的小兔 · 发表于 2010-10-5 12:39:26

谢谢小龙

条件2里面的意思是65+ 的人群里 20%男和10%女被雇佣，所以和总人数里男女各自的人数是不一样的，对吧？

还有怎么个加权平均呢？

还是不太明白，不好意思数学很烂

快乐小龙 · 发表于 2010-10-5 12:54:48

就是这个意思条件2的人数肯定小于男女各自的人数

M给的解释里写出的那个公式就是一个加权平均公式吗，百分比就是权重。
你把这条规则记住就好了

the weighted average MUST lie somewhere from 10% (which would be the "average" if everyone 65+ years old were female) to 20% (which would be the "average" if everyone in that demographic were male). 就是说不可能低于这个区间的

我的数学不也好的，共勉

另一道prep DS

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