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标题: 这道概率题好奇怪讶，请大家帮帮忙 [打印本页]

作者: hebeqiao 时间: 2008-1-6 11:01
标题: 这道概率题好奇怪讶，请大家帮帮忙

Q2:从条件1和2 都可得出women 的人数大于5 ，因此p<1/2呀，怎么回事呢？

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 than1/10 .

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.

Answer: e

[此贴子已经被作者于2008-1-6 11:03:00编辑过]

作者: afflare 时间: 2008-1-6 11:17
The answer E is correct. From condition2, you can get the number of men<=3. So if the number of women is 7, P can be caculated to 7/15.

作者: hebeqiao 时间: 2008-1-6 11:56

But when men<=3, women can be 7, then the probility of two women being selected is comination of 2 from 7=21, the whole probility is combination of 2 from 10=45, then p=21/45, which is also<1/2, so we should still choose d. Am I wrong somewhere?

作者: hebeqiao 时间: 2008-1-6 12:00
oh, I get it, women can be 8, then p=28/45, so e. Thanks a lot!!

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