1JJ，在线等！

donna2003

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。

justag

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

donna2003

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

arthur

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？

donna2003

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？