长时间不看数学有点小忘了，这两道题大家帮我看下哈~谢谢！

魔法城市 · 发表于 2010-10-10 11:44:23

很长时间没看数学了，概率有点模糊，这两道题目一下子没有思路了，
麻烦大家帮忙看一下告诉我怎么解哈，谢谢啦！！

第一题：
There are 11 women and 9 men in a certain club.If the club is to select a committee of 2 women and 2 men, how many different such committees are possible?

A.120

B.720

C.1,060

D.1,520

E.1,980

Answer: E

第二题：
There are 8 magazines lying on a table; 4 are fashion magazines and the other 4 are sports magazines.If 3 magazines are to be selected at random from the 8 magazines, what is the probability that at least one of the fashion magazines will be selected?

A.1/2

B.2/3

C.32/35

D.11/12

E.13/14

Answer: E

Thank you !

第二题：
There are 8 magazines lying on a table; 4 are fashion magazines and the other 4 are sports magazines.If 3 magazines are to be selected at random from the 8 magazines, what is the probability that at least one of the fashion magazines will be selected?

A.1/2

B.2/3

C.32/35

D.11/12

E.13/14

Answer: E

Thank you !

魔法城市 · 发表于 2010-10-10 11:45:03

重复了一道不好意思啊~

fanfantastic · 发表于 2010-10-10 11:59:10

这里的格式我打不出来啊~

第一题：
从11 women挑出2个，从9 men中挑出两个。是组合问题。
C11,2 * C9，2=55*36=1980
11和9是下标，2是上标。

第二题：
“至少一个”这种题可以从反面想，用1减去“一个都不”的可能性。
这道题里，一本fashion magazine也不被挑出的，也就是3本书都从sports magazines中挑出的可能性是C4,3 / C8,3 = 4 / 56 = 1/14
用1减去之后就是13/14啦~

希望对你有帮助~

魔法城市 · 发表于 2010-10-10 13:43:06

非常感谢！发现我是要多花点时间在数学上了呵呵

ZKRAP · 发表于 2010-10-10 18:19:40

二楼正解无误

魔法城市 · 发表于 2010-10-12 09:09:26

长时间不看数学有点小忘了，这两道题大家帮我看下哈~谢谢！

所属分类: GMAT考试

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