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Math Help - number of combinations

  1. #1
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    number of combinations

    Please tell how you arrived there soi understand it, that is the most imporant thing.

    How many ways can sierra select 3 movies to rent from the top 10 rentals?
    A.720 ways, B.240 C. 90 ways D.120 ways
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  2. #2
    MHF Contributor arbolis's Avatar
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    I think it's 10 chose 3. That is, \frac{10!}{(10-3)!3!}=120. To do it, I didn't think a lot. I mean the formula I gave you is very well known and useful in cases like yours here. It means, if you have 10 elements, how many ways are they if you want to pick 3 of them? This is exactly your problem. So I guess you'll get used to it after having done every kind of problems.
    More generally, if there is a total of n element and you want to pick up m elements, the total possibilities are \frac{n!}{(n-m)!m!}. You should learn this formula and check out your notes, it is probably there and well explained.
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  3. #3
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    Thank you
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  4. #4
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    Quote Originally Posted by phil2611 View Post
    Thank you

    hello me
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