BCECE Engineering BCECE Engineering Solved Paper-2003

  • question_answer
    Let    \[~0<P(A)<1,0<P(B)<1~\] and \[P(A\cap B)=P(A)+P(B)-P(A)P(B),\]then:

    A) \[P(B/A)=P(B)-P(A)\]

    B)                   \[P({{A}^{c}}\cup {{B}^{c}})=P({{A}^{c}})+P({{B}^{c}})\]

    C)                   \[P{{(A\cup B)}^{c}}=P({{A}^{c}})P({{B}^{c}})\]

    D)                   \[P(A/B)=P(A)+P({{B}^{c}})\]

    Correct Answer: C

    Solution :

    Since,\[P(A\cap B)=P(A)P(B)\] \[\Rightarrow \]A and B are independent events \[\Rightarrow \]\[{{A}^{c}}\]and\[{{B}^{c}}\]will also indent events                 Hence, \[P{{(A\cup B)}^{c}}=P({{A}^{c}}\cap {{B}^{c}})\]                                 \[=P({{A}^{c}})\cap P({{B}^{c}})\]                 \[\therefore \]Option (c) is correct. Note: If two events A and B are independent, then its complement is also independent.


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