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Thread: Hi guys!Need help with combinatorics problem!

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    Trying to make mom and pop proud
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    Exclamation Hi guys!Need help with combinatorics problem!

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    How many two-element subsets of (1,2,3,4) are there that do not contain the pair of elements 2 and 4?
    a) 1
    b)2
    c)4
    d)5
    e)6

    How did you solve? Explanation please!

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    An Urch Guru Pundit Swami Sage
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    Re: Hi guys!Need help with combinatorics problem!

    You can do this by taking 4C2 - 1.

    Or, this is a pretty easy problem to just go through the combinations. Given the choices, you have at most 6 combinations to identify.

    Here are the combos:

    1,2
    1,3
    1,4
    2,3
    2,4
    3,4

    Look six combinations, but don't count (2,4). So 5 different subsets.

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    Re: Hi guys!Need help with combinatorics problem!

    Thanks!

    Quote Originally Posted by YaSvoboden View Post
    You can do this by taking 4C2 - 1.

    Or, this is a pretty easy problem to just go through the combinations. Given the choices, you have at most 6 combinations to identify.

    Here are the combos:

    1,2
    1,3
    1,4
    2,3
    2,4
    3,4

    Look six combinations, but don't count (2,4). So 5 different subsets.

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