概率难题！！！！ gwd23 - Q30

gaode · 发表于 2007-7-12 02:36:00

Q30:

There are 8 books on a shelf, of which 2 are paperbacks and 6 are hardbacks. How many possible selections of 4 books from this self include at least one paperback?

A. 40

B. 45

C. 50

D. 55

E. 60

Answer: C

请 NN解释答案 Why C. 多谢。

[此贴子已经被作者于2007-7-12 3:04:13编辑过]

snoopy55 · 发表于 2007-7-12 09:10:00

以下是引用gaode在2007-7-12 2:36:00的发言：

Q30:

There are 8 books on a shelf, of which 2 are paperbacks and 6 are hardbacks. How many possible selections of 4 books from this self include at least one paperback?

A. 40

B. 45

C. 50

D. 55

E. 60

Answer: C

请 NN解释答案 Why C. 多谢。

有一本的取法：c(6,3)Xc(2,1)=40

有2本的取法：c(6,2)=15 一共55种，答案是D

fancyfang · 发表于 2007-7-12 14:09:00

I choose D too, why is C?

sammy生米 · 发表于 2007-7-12 21:25:00

这题答案错，应该是D的

popofeeling · 发表于 2007-7-12 21:45:00

答案是D， C（4，8）-C（4，6）排除法做

gaode · 发表于 2007-7-12 23:56:00

多谢NN们! 祝天天好运！！！

shiguang · 发表于 2007-7-13 01:36:00

D The answer is false.

genius156 · 发表于 2009-8-1 23:06:00

pinpin117 · 发表于 2009-8-1 23:15:00

对的~~~答案是D，

我的方法是C8，4-C6，4=70-15=55

概率难题！！！！ gwd23 - Q30

概率难题！！！！ gwd23 - Q30

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