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Math Help - [SOLVED] Calculate the following probabilities

  1. #1
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    Exclamation [SOLVED] Calculate the following probabilities

    Let A and B be events with P(A) = 2/5, P(B) = 1/2, P(AnB) = 3/20. Calculate the
    following probabilities.
    i) P(Ac) (means probabilty of Not A)
    ii) P(A U B)
    iii) P(Ac n B)
    iv) P(B\A)

    I know:
    1) P(Ac)= 1-2/5= 3/5
    2)P(A U B)= 2/5+1/2-3/20 = 3/4


    But i am stuck on
    iii) P(Ac n B)
    iv) P(B\A)

    Can anyone help me please
    Last edited by the1u2001; October 12th 2008 at 07:12 AM.
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  2. #2
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    How are you using P(A\B)? Do you mean A not B or A given B?
    In either case you are mistaken about the value P(A \cap B) unless that is what P(A\B).
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  3. #3
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    Quote Originally Posted by Plato View Post
    How are you using P(A\B)? Do you mean A not B or A given B?
    In either case you are mistaken about the value P(A \cap B) unless that is what P(A\B).
    Yeah sorry about that i meant = 3/20
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  4. #4
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    \begin{gathered}<br />
  P(B) = P(B \cap A) + {\color{blue}P(B \cap A^c )} \hfill \\<br />
  {\color{blue}P(B \cap A^c )} = P(B) - P(B \cap A) \hfill \\ <br />
\end{gathered}
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