GWD14-2

yinhang_1217

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  1/2 of the 10 employees are women.

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

                  

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案选B。

明显有问题啊！令男生n个人，则有(n/10)*((n-1)/9)<1/10

算出来n<=3，如果n=3，那么两次都是女生的概率就是(7/10)*(6/9)=42/90<1/2

如果n=1或者2，那么两次都是女生的概率大于1/2

所以应该选E啊！

chenmengmeng

同意选E。