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Math Help - probability

  1. #1
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    probability

    (n ) = 210 , find the value of n, where n ≥ 2.
    . 2

    sorry the 2 is supposed to be under n inside the bracket , as in n choose 2. or nC2.

    i have no idea how to do this i got it for homework despite the fact that we never did it in class.
    Last edited by amyl95; March 22nd 2013 at 04:07 PM.
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  2. #2
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    Re: probability

    Quote Originally Posted by amyl95 View Post
    (n ) = 210 , find the value of n, where n ≥ 2.
    . 2 sorry the 2 is supposed to be under n inside the bracket , as in n choose 2. or nC2.
    i have no idea how to do this i got it for homework despite the fact that we never did it in class.
    Can you solve \frac{n(n-1)}{2}=210 for n~?
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  3. #3
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    Re: probability

    ya then i get n=-20 or n=21, so that must mean that n=21 if it in the question it states that n ≥ 2. thanks but i just don't get where you got n(n-1)/2 ?
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  4. #4
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    Re: probability

    Amy 195

    Pls study the formula of combinations. the formula that gives you how many combinations you will get if you have n -distict objects and you combine them by 2 is the one that Plato gave you...
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