[fnord_too]

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This is a homework problem that i can not figure out.

An elevator with 9 passengers stops at 5 different floors. If we are only interested in the passengers who get off together, how many possible distributions are there?

Thanks in advance for any help.

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Assumption: At least one person gets off at every stop.
Assumption: Which stop people get off at does not matter (that is, say two people get off at a stop, the only important thing is that these two people got off at the same stop, not that they got off at a specific stop.)

Since at least 1 person gets off at each stop, label the first person off at stop 1 "1", the first person off at stop 2 "2", etc.

(Arbitrarily lable the last four passengers 6, 7, 8, and 9)

How many ways can 4 distinct people get off at 5 stops? (If you have trouble with this bit, ask after you have chewed on it for a while. If the assumptions are invalid, let me know).