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Math Help - [SOLVED] Counting principles

  1. #1
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    [SOLVED] Counting principles

    I have had difficulty understanding this topic with Union and Mutually exclusive involved. Can anyone explain what is the N( X U Y) and the N ( X *upside down U* Y) is? the book is confusing me because they are using it interchangeably

    Also I have a question on my hw (I will use the letter i for the upsidedown U)

    Suppose two fair dice are rollled, Find N(X U Y) and N(X i Y)

    X=the first die shows 6
    Y=the sum of the dice is 10
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  2. #2
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    Quote Originally Posted by something3k View Post
    I have had difficulty understanding this topic with Union and Mutually exclusive involved. Can anyone explain what is the N( X U Y) and the N ( X *upside down U* Y) is? the book is confusing me because they are using it interchangeably

    Also I have a question on my hw (I will use the letter i for the upsidedown U)

    Suppose two fair dice are rollled, Find N(X U Y) and N(X i Y)

    X=the first die shows 6
    Y=the sum of the dice is 10
    U means union, which means cases X OR Y is satisfied.
    In your example, it means the first die is 6 or the sum of the dice is 10.
    So X U Y will be (6, 1) (6, 2) (6, 3) (6, 4) (6, 5) (6, 6) (4, 6) (5, 5)
    There are 8 cases. So N (X U Y) is 8.

    inverted U means intersection, which means cases X AND Y are satisfied.
    In your example, it means that the first die is 6 and the sum of the dice is 10.
    So X intersect Y will be only (6, 4)
    There is only 1 case. So N (X intersect Y) is 1.

    Hope this helps.
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  3. #3
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    yea i had to read that over like 5 times and other stuff but i think im getting it, thanks
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