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combination vs permutation [#permalink]
16 Jun 2010, 18:26

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the followings are combination and permutation questions: 1) if seven people board an airport shuttle with only three available seats, how many different seating arrangements are possible? 2) if three of seven standby passengers are selected for a flight, how many different combinations of standby passengers can be selected?

it seems to me that the questions are the same--select 3 people out of a group of 7 people. however, the explanations state that the 1st one is permutation and the 2nd one is combination. how do we know if the order matters when the questions don't explicitly state it? any clarification will be appreciated! Thanks!

Re: combination vs permutation [#permalink]
16 Jun 2010, 18:40

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The key words are "arrangement", implying "Permutation", and "combinations", implying exactly as it suggests. In the first case the answer is 7P3 (the seating arrangement matters: ABC and CBA are different). Wheras in the second case, the answer is 7C3 (the order of choosing doesnt matter: orders ABC and CBA are same).

Hope this helps!

gmatclubot

Re: combination vs permutation
[#permalink]
16 Jun 2010, 18:40