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Proabity: Concept

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Proabity: Concept

by \'manpreet singh » Wed Nov 14, 2012 10:22 pm
q.1 If seven people board an airport shuttle with only three available seats, how
many different seating arrangements are possible? (Assume that three of
the seven will actually take the seats.)

q.2 If three of seven standby passengers are selected for a flight, how many
different combinations of standby passengers can be selected?

Please explain how are these 2 questions different?I need a comparison as i feel a little unclear about the concept here?
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by eaakbari » Wed Nov 14, 2012 11:38 pm
If I asked you to cite an example on the difference between permutations & combinations, your question is the perfect answer.

In (1) , they are asking for the arrangement ABC is different from BCA. They keyword here is 'arrangement'. Thats when you know its a permutation.
Answer = n(P)r

In (2), BCA is no different from ABC. Hence its a combination.
Answer = n(C)r
Whether you think you can or can't, you're right.
- Henry Ford
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by \'manpreet singh » Thu Nov 15, 2012 12:01 am
eaakbari wrote:If I asked you to cite an example on the difference between permutations & combinations, your question is the perfect answer.

In (1) , they are asking for the arrangement ABC is different from BCA. They keyword here is 'arrangement'. Thats when you know its a permutation.
Answer = n(P)r

In (2), BCA is no different from ABC. Hence its a combination.
Answer = n(C)r

Thanks for your quick repsonse,
But that's whats confusing me.....forget about permutation and combination.If we take to counting method.How are you saying that in first case ABC is different from BCA, meaning they are distinguihable from one another and in second question ABC is same as BCA,meaning they are undistinguishable . How are you conculding these two statements, i basically need clarity on that.

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Singh
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