总结| 几道有争议的数列题一月JJ....到现在好没有一致答案

cageshi117

觉得74应该是D

tqfriend

以下是引用lisese在2009-1-19 11:17:00的发言：

74（DS）一群人，X%说是有A，y%说有B，求说只有A没B的？
  

1：有说B没A的是Z

2：说既有A又有B的是W.

机经同学说选D了。

should be C

for A: you have A or not A

for B: you have B or not B

let X%=20%, y%=40%

1: 有说B没A的是Z, let Z=15
we do not know the total number of people in this group, so 1 alone is not conclusive

2: 说既有A又有B的是W, let W=20
for the same reason as that of 1, 2 alone is not conclusive

1+2: (15+20)/ 0.4=total, so total can be determined, so x%* total is known, so the rest of data is known

so answer is C

－－－－－－－－－－－－－－－－－－－－－－－－－－

偶同意D！

不是应该是C吗。。。。。急。。。。

xiaoping0000

以下是引用wangxiaoqing在2009-1-19 8:41:00的发言：

74（DS）一群人，X%说是有A，y%说有B，求说只有A没B的？

  

 

1：有说B没A的是Z

 

2：说既有A又有B的是W.

 

机经同学说选D了。

should be C

for A: you have A or not A

for B: you have B or not B

let X%=20%, y%=40%

1: 有说B没A的是Z, let Z=15
we do not know the total number of people in this group, so 1 alone is not conclusive

2: 说既有A又有B的是W, let W=20
for the same reason as that of 1, 2 alone is not conclusive

1+2: (15+20)/ 0.4=total, so total can be determined, so x%* total is known, so the rest of data is known

so answer is C

 

严重同意