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标题: 1JJ，在线等！ [打印本页]

作者: donna2003 时间: 2002-12-28 18:52 标题: 1JJ，在线等！

Math:
(1) Totally 10 people, including Harry. Pick 1 out of 10 for president, then pick 1 out of 9 for secretary, pick 1 out of 8 for treasurer. What is the probability that Harry will be picked for either secretary or treasurer?

请确认。

作者: donna2003 时间: 2002-12-28 18:55

如果是Neither secretary Nor treasurer答案是4/5还是1/10？
如果是 ONLY secretary 答案是1/10，对吗？

作者: arthur 时间: 2002-12-28 19:24

如果是Neither secretary Nor treasurer答案是4/5
如果是either secretary or treasurer答案是1/5
对吗？

作者: donna2003 时间: 2002-12-28 19:32

如果是either secretary or treasurer，是1/10+1/10=1/5，你是这么算的吗？

作者: justag 时间: 2002-12-29 01:44

I think so.

Either..or... [(9*1*8)+(9*8*1)]/(10*9*8)=1/5,
Neither...nor...1-1/5=4/5

Or think like this: Neither S nor T nor P with p=9*8*7/10*9*8=7/10 or Neither S nor T but P with p=(1*9*8)/(10*9*8)=1/10. In sum, 4/5

So, Haryy can be either S or T with p=1/5; neithor S nor T with p=4/5

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