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Math Help - mutually exclusive problem

  1. #1
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    mutually exclusive problem

    Hi I'm having trouble with this question:

    Let A and B be independent events, where P(A) = 0 and P(B)=x
    a) write down an expression for P(A ∩ B)
    b) Given that P(A U B) = 0.8,
    i)find x
    ii) find P(A ∩ B)
    c) Hence, explain why A and B are not mutually exclusive

    Any help is greatly appreciated. =)
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  2. #2
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    Quote Originally Posted by adsfdgfh View Post
    Hi I'm having trouble with this question:

    Let A and B be independent events, where P(A) = 0 and P(B)=x
    a) write down an expression for P(A ∩ B)
    b) Given that P(A U B) = 0.8,
    i)find x
    ii) find P(A ∩ B)
    c) Hence, explain why A and B are not mutually exclusive

    Any help is greatly appreciated. =)
    Substitute what you're given into the usual formula \Pr(A \cup B) = \Pr(A) + \Pr(B) - \Pr(A \cap B) and solve for \Pr(A \cap B).
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  3. #3
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    i've done that and got P(A∩B) = 0 which would mean they ARE mutually exclusively. Im pretty sure i did something wrong but can't seem to find it.
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  4. #4
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    Quote Originally Posted by adsfdgfh View Post
    i've done that and got P(A∩B) = 0 which would mean they ARE mutually exclusively. Im pretty sure i did something wrong but can't seem to find it.
    If P(A) = 0 (which is what you have stated in your first post) then obviously P(A∩B) = 0 ....

    But if P(A) = 0 I wouldn't have thought that discussing the mutual exclusivity of A and B made much sense ....
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  5. #5
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    Quote Originally Posted by mr fantastic View Post
    If P(A) = 0 (which is what you have stated in your first post) then obviously P(A∩B) = 0 ....

    But if P(A) = 0 I wouldn't have thought that discussing the mutual exclusivity of A and B made much sense ....
    sorry, i just found out there was actually a typo in the assignment. P(A) is actually 0.6, which makes the question a lot easier to do
    thanks for all your help though
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