一道GWD的数学概率題請大家帮我看看～～

bernadotte

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.
Ans. E

自己分析下，大家看思路对不对，

条件一下，最少女人为6个，则同时2女概率为C(6,2)/C(10,2)=1/3；最多10个女的，概率100%；即1/3<p<1.



条件二下，设同时2男概率为m，则m/C(10,2)<1/10，推出m<4.5，即这种情况少于等于4中组合，从而推出男人为2人，或者3人。

若男人为2人，推出女人为8人，得C(8,2)/c(10,2)=28/45>1/2;

若男人为3人，推出女人为7人，得p为C（2，7）/c(10,2)=7/15<1/2

故而，条件二也不充分。

结合条件1，2同样不能得出p的值，故选择e。

nicolewitch

what are the two numbrs in the two conditions?
men less than what and more than what women....

bernadotte

什么啊 不懂

huiguo85

你的两个条件都不完整，所以做不出来

bernadotte

sorry我重新发

heimiheimi

答案：E 排列组合问题

bernadotte

ding