RAJASTHAN ­ PET Rajasthan PET Solved Paper-2012

  • question_answer
    If\[P(A)=P(B)=x\]and \[P(A\cap B)=P(A'\cap B')=\frac{1}{3},\] then\[x\]is equal to

    A)  \[\frac{1}{2}\]

    B)  \[\frac{1}{3}\]

    C)  \[\frac{1}{4}\]

    D)  \[\frac{1}{6}\]

    Correct Answer: A

    Solution :

    Given that, \[P(A)=P(B)=x\] and   \[P(A\cap B)=P(A'\cap B')=1/3\] \[\therefore \] \[P(A'\cap B')=1-P(A\cup B)=1/3\] \[\Rightarrow \] \[P(A\cup B)=2/3\] Now, \[P(A\cup B)=P(A)+P(B)-P(A\cap B)\] \[\Rightarrow \] \[\frac{2}{3}=x+x-\frac{1}{3}\] \[\Rightarrow \] \[2x=1\] \[\Rightarrow \] \[x=\frac{1}{2}\]


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