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How to use the P-none for Probability

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How to use the P-none for Probability

by melcra » Tue Dec 30, 2008 7:15 am
A certain club has 10 memebers, including Harry. One of the 10 of the 10 memebers is to be chosen at random to be the president, one of the remaining 9 members is to be chosen at random to be the secretary, and one of the remaining 8 members is to be chosend at random to be treasurer. What is the probability that Harry will be either the member chosen to be the secretary or the member chosen to be the treasurer?

A) 1/720
B) 1/80
C) 1/10
D) 1/9
E) 1/5
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by Ian Stewart » Tue Dec 30, 2008 7:30 am
Harry is just as likely as anyone else to be selected for one of the two positions, so the answer is 2/10 = 1/5.

This question is from the diagnostic test at the beginning of the OG, and I do not understand why their solution goes on for several paragraphs.
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by melcra » Tue Dec 30, 2008 8:06 am
Thank you, I have no idea either why so many paragraphs. I think having that many paragraphs confused me. Thanks again for your help. You make it seem easy. :D
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