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Thread: How many combinations?

  1. April 5th 2010, 08:07 AM #1
    Showcase_22
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    How many combinations?

    Suppose I have a_1,a_1,a_2,a_3,a_4,a_5,a_5. How many ways can I arrange them?

    If I have a_1,a_1,a_2,a_3,a_4,a_5,a_6, then I would have ^7C_2 combinations. What do I do if I have another group of two?

    Would it be ^7C_3.^4C_2 (ie. the number of ways of picking a_2,a_3,a_4 multiplied by the number of ways of rearranging a_1,a_1,a_5,a_5?
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  2. April 5th 2010, 08:26 AM #2
    Plato
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    Quote Originally Posted by Showcase_22 View Post
    Suppose I have a_1,a_1,a_2,a_3,a_4,a_5,a_5. How many ways can I arrange them?
    I do not understand this question fully.
    But the answer to the quoted part is \frac{7!}{(2!)^2}
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