一道来自manhattan的题目，望NN们来帮帮我，谢谢~

evelyn205205 · 发表于 2011-7-20 16:24:49

In a room filled with 7 people, 4 people have exactly 1 sibling in the room and 3 people have exactly 2 siblings in the room. If two individuals are selected from the room at random, what is the probability that those two individuals are NOT siblings?

答案是16/21.
这道题怎么个思路做啊？

bennywang2usa · 发表于 2011-7-20 16:31:10

题目说4个人有1个兄弟姐妹，3个人有2个兄弟姐们。根据最后题干可以看出，这7个人互相有亲戚关系哦~

yaner11 · 发表于 2011-7-20 16:58:20

关系是这样的：

一组： A, B,
二组： C, D,
三组： E, F, G

3*4+ 2* 2=16
7取2等于21

evelyn205205 · 发表于 2011-7-20 17:52:01

谢谢啦，你的解释很清晰~

evelyn205205 · 发表于 2011-7-20 17:57:48

谢谢！

一道来自manhattan的题目，望NN们来帮帮我，谢谢~

所属分类: GMAT考试

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