GWD 05-02

efficiency

Q2:

If 2 different representatives are to be selected at random from a group of 10 employees and if p is the probability that both representatives selected will be women, is p >1/2 ?

(1) More than 1/2of the 10 employees are women.

(2) The probability that both representatives selected will be men is less than 1/10

请问这道题怎么做啊？

elitist

应该是选E把！

从10个人中选2个，都为女性的概率为P， 问P>1/2?

1）10个人中最少有1/2的女性 P>=C(2,5)/C(2,10)>=4/9,不充分

2）都选男性的概率少于1/10 P<=1-1/10=9/10，不充分

fhhrewr

楼上的2)的解释有问题。都选男性的概率小于1/10，那么9/10应该是有一男或没有男的

我想应该是：设男人有n个，(n/10)*[(n-1)/9]<1/10

n(n-1)<9，则n最多只能有3个。

当有3个男人，即有7个女人的时候，全女的概率为(7/10)*(6/9)=14/30<1/2，所以不充分。。。