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请教一道GWD数学题

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楼主
发表于 2008-5-30 11:09:00 | 只看该作者

请教一道GWD数学题

DS:

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)     More than  of the 10 employees are women.

(2)     The probability that both representatives selected will be men is less than .

我选的E,但我看答案是B,不知道是为什么,根据条件B,男人可以是2 个和3个,如果是2个男人,8个女人,P大于1/2, 但如果是3男7女,P小于1/2,根据无法推出结论啊,请教NN指点,谢谢。

沙发
发表于 2008-5-30 11:14:00 | 只看该作者
MM,答案是不是抄全了? 条件2,2个人都会是男生的比例小于....,还是题目就是这样的?
板凳
发表于 2008-5-30 11:25:00 | 只看该作者

楼主题目没全, 这个题目应该是

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

地板
发表于 2008-5-30 11:27:00 | 只看该作者
汗..忘记解答了...这个题目就应该是选E啊...楼主是不是看错答案了....
5#
 楼主| 发表于 2008-5-30 11:29:00 | 只看该作者

对不起啊,是没抄全,条件2是BOTH MALE 小于1/10,还有另外一题:

Tom, Jane, and Sue each purchased a new house.  The average (arithmetic mean) price of the three houses was $120,000.  What was the median price of the three houses?

(1)     The price of Tom’s house was $110,000.

(2)     The price of Jane’s house was $120,000.

我选B,答案是E, 我直晕啊,是答案错了,还是我错了啊,请指教。谢谢

6#
发表于 2008-5-30 11:36:00 | 只看该作者

汗...mm你两次说法是反着的啊...

这个题目(1), (2)都不充分, 合起来也不充分...所以选择E啊...你在顶楼已经说过了啊..B无法退出答案的.啊...

7#
发表于 2008-5-30 11:37:00 | 只看该作者
答案是E
(1)假设一个极限,所有的人都是女人,则p=100%,如果6个女人,则p=C2,6/C2,10>1/2
(2)C2,X/C2,10<1/10, x(x-1)<9,x=0,x=1,x=2,x=3
女人数就是>=7
最小几率是C2,7/C2,10=7/15<1/2
如果女人数是8,p>1/2
你是对的
8#
发表于 2008-5-30 11:41:00 | 只看该作者
以下是引用shelleyzheng在2008-5-30 11:29:00的发言:

对不起啊,是没抄全,条件2是BOTH MALE 小于1/10,还有另外一题:

Tom, Jane, and Sue each purchased a new house.  The average (arithmetic mean) price of the three houses was $120,000.  What was the median price of the three houses?

(1)     The price of Tom’s house was $110,000.

(2)     The price of Jane’s house was $120,000.

我选B,答案是E, 我直晕啊,是答案错了,还是我错了啊,请指教。谢谢

又要汗一次...没看清居然是另外一道题目...这个题目是选B, 不知道MM对的是那个版本的答案......呵呵....

9#
发表于 2008-5-30 11:48:00 | 只看该作者

Tom, Jane, and Sue each purchased a new house.  The average (arithmetic mean) price of the three houses was $120,000.  What was the median price of the three houses?

(1)     The price of Tom’s house was $110,000.

(2)     The price of Jane’s house was $120,000.

我选B,答案是E, 我直晕啊,是答案错了,还是我错了啊,请指教。谢谢



答案是B,同意

10#
发表于 2008-5-30 17:49:00 | 只看该作者
以下是引用stavan在2008-5-30 11:25:00的发言:

楼主题目没全, 这个题目应该是

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

如果题目是这个的话,p是一定>1/2的。

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