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Question with intersects and complements.

  1. Sep 26, 2008 #1
    Ok, first post.
    So I have this question, which goes something like this...
    P(A)=0.3, P(B)=0.3, P(C)=0.7
    P(AnB^c)=0.2, P(AnC^c)=0.2, P(AnBnC)=0

    Find P((AnB)U(AnC))

    (Where; n =intersect, U union, ^c = complement.)

    Personally my thoughts are..
    P(AnBnC)=0. Therefore mutually exclusive.

    And then Because probability cannot be negative. I think that leads to P(AnB)=0,P(AnC)=0 & p(BnC)=0.
    Which couldnt be right, As that would give P((AnB)U(AnC)) = 0U0 = 0.

    My major concern is how do I change P(AnC^c) & P(AnB^c) to something useful!

  2. jcsd
  3. Sep 26, 2008 #2
    Ive got
    P(A)- P(AnB^c) + P(A)- P(AnC^c)= P((AnB)U(AnC))

    Anyone want to double check me?
  4. Sep 26, 2008 #3


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    Science Advisor
    Gold Member

    It's correct. Do you understand how? Also you obviously can get a number from it.
  5. Sep 26, 2008 #4
    Awesome. Yeah, I understand how. Just had a block a guess.
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