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Old 07-31-2007   #2

Join Date: Oct 2006
Posts: 822

Doesn't it depend on how many people there are? Well, I guess I'll let that be Y. Also, I assume you start at the floor below the first.
(i) The possible values range from 0 to Y
(ii) For 0- Basically each person has a chance of not going off at floor 1, and there are X people.
Similarly, for 1 (I'm kind of guessing on this) it's . ( Or should that be multiplied by Y?)That's a hint, I don't want to do it all, so the rest is yours
(iii)You expect of the poeple to get off at each floor, so the answer is

Hopefully I got some of these right...

Last edited by Sillysidley; 07-31-2007 at 06:10 PM.. Reason: Thought it was AoPS...
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