ChaseDream

标题: 今天一道数学题把我给难住了! [打印本页]

作者: splendor 时间: 2004-12-28 11:49
标题: 今天一道数学题把我给难住了!
Each document has both a paper copy and an electrical copy. Of the paper copies that are inaccurate, 60% also has an inaccurate electrical copies. Of the electrical copies that are inaccurate, 75% also has an inaccurate paper copy. 3% of documents has both inaccurate paper copy and electric copy. What's the probability a randomly drawn document has both accurate paper and accurate electrical copy?

作者: charmant 时间: 2004-12-28 12:51

记E为事件Electrical copy错误,P为Paper copy错误

由题意知：P(P|E)=75%, P(E|P)=60% (EP)=3%

根据条件概率公式：P(P|E)=P(EP)/P(E)

所以P(E)=P(EP)/P(P|E)=3%/75%=4%

同理可得P(P)=5%

所以P(E+P)=P(P)+P(E)-P(EP)=6%

所以Both accurate的probability=1-6%=94%

用文氏图应该是

[attachimg]24246[/attachimg]

[此贴子已经被作者于2004-12-28 13:12:24编辑过]

作者: blackhorse 时间: 2004-12-28 12:53

请修改标题，注明出处，参考
【发贴必读】格式，编辑，查找功能解释
http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=31635&page=1

感谢你的理解和支持！

而且这道题目很多人问过了，建议你搜索以前的讨论。

作者: iloveqi 时间: 2004-12-28 13:05

以下是引用splendor在2004-12-28 11:49:00的发言：
Each document has both a paper copy and an electrical copy. Of the paper copies that are inaccurate, 60% also has an inaccurate electrical copies. Of the electrical copies that are inaccurate, 75% also has an inaccurate paper copy. 3% of documents has both inaccurate paper copy and electric copy. What's the probability a randomly drawn document has both accurate paper and accurate electrical copy?

好像本月几经里见过，inaccurateP&E占总的3%，又分别在inaccurateP和inaccurateE中占60%和75%，由此，可以求出inaccurateP占总的：3%除以60%=5%，inaccurateE占总的：3%除以75%=4%，所以accurateP&E=1-5%-4%+3%=94%

作者: blackhorse 时间: 2004-12-28 21:03

以下是引用iloveqi在2004-12-28 13:05:00的发言：

好像本月几经里见过，inaccurateP&E占总的3%，又分别在inaccurateP和inaccurateE中占60%和75%，由此，可以求出inaccurateP占总的：3%除以60%=5%，inaccurateE占总的：3%除以75%=4%，所以accurateP&E=1-5%-4%+3%=94%

数学不错，鼓励！！！

作者: zhaoshujuanw 时间: 2005-1-11 11:58

Thanks ,big NN

作者: 爱维的天 时间: 2005-1-11 12:12

以下是引用blackhorse在2004-12-28 12:53:00的发言：

请修改标题，注明出处，参考
【发贴必读】格式，编辑，查找功能解释
http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=31635&page=1

感谢你的理解和支持！

而且这道题目很多人问过了，建议你搜索以前的讨论。

我推这个…

作者: soaring 时间: 2005-1-17 09:43
charmant真牛~

作者: feichiwu 时间: 2005-1-24 22:43

低等数学解法：设一共有100m，其中纸纪录错误的y个，电子纪录错误x个。75%x=3%*100m 所以，x=4m,同理，y=5m

没错的100m-5m-4m-3m=94m

94m\100m=94%

欢迎光临 ChaseDream (https://forum.chasedream.com/)