[求助]天山4-24

爱维的天

天山4-24请问
Factor                                   ercent of Respondents
User-friendly                                       56%
Fast response time                                  48%
Bargain prices                                      42%

The table gives three factors to be considered when choosing an Internet service provider
and the percent of the 1,200 respondents to a survey who cited that factor as important. If
30 percent of the respondents cited both “user-friendly” and “fast response time,” what is
the maximum possible number of respondents who cited “bargain prices,” but neither
“user-friendly” nor “fast response time?”
A. 312
B. 336
C. 360
D. 384
E. 420

如何求解?
Ans = A

[此贴子已经被作者于2004-12-18 20:41:16编辑过]

beautywawa

ANS:A是嗎?

爱维的天

Sorry... I forgot to give the correct answer. The answer is A...u r right

whitesand

U + F + B - UnF - UnB - BnF + UnFnB = 1

B- UnB- BnF =1- F- U+ UnF - UnFnB = 1- 56%- 48% +30%  (UnFnB=0, 值最大)
B- UnB- BnF =26%

1200x26%=312

我一边看"美食大三通"一边写这题, 写着写着就忘了, 花了很长时间

[此贴子已经被作者于2004-12-18 20:45:47编辑过]

爱维的天

Thanks ...  I see.

beautywawa

以下是引用whitesand在2004-12-18 20:44:00的发言：

U + F + B - UnF - UnB - BnF + UnFnB = 1

B- UnB- BnF =1- F- U+ UnF - UnFnB = 1- 56%- 48% +30%  (UnFnB=0, 值最大)
B- UnB- BnF =26%

1200x26%=312

我一边看"美食大三通"一边写这题, 写着写着就忘了, 花了很长时间

白沙,妳也看阿,,我也看耶,,還不錯說,,,

cdoublesok

感觉这里的UnFnB应该是加上两倍吧,

虽然等于零以后不影响结果,

参考书没在手边,请其他xdjm确认一下

foreinter

以下是引用whitesand在2004-12-18 20:44:00的发言：

U + F + B - UnF - UnB - BnF + UnFnB = 1

B- UnB- BnF =1- F- U+ UnF - UnFnB = 1- 56%- 48% +30%  (UnFnB=0, 值最大)
B- UnB- BnF =26%

1200x26%=312

我一边看"美食大三通"一边写这题, 写着写着就忘了, 花了很长时间