Manipal Engineering Manipal Engineering Solved Paper-2009

  • question_answer
    Suppose that\[{{E}_{1}}\]and\[{{E}_{2}}\]are two events of\[a\]random experiment such that\[P({{E}_{1}})=\frac{1}{4}\],\[P({{E}_{2}}/{{E}_{1}})=\frac{1}{2}\] and\[P({{E}_{1}}/{{E}_{2}})=\frac{1}{4}\], observe the lists given below
    List-I List-II
    (A) \[P({{E}_{2}})\] (i) 1/4
    (B) \[P({{E}_{1}}\cup {{E}_{2}})\] (ii) 5/8
    (C) \[P({{\bar{E}}_{1}}/{{\bar{E}}_{2}})\] (iii) 1/8
    (D)\[P({{E}_{1}}/{{\bar{E}}_{2}})\] (iv) 1/2
      (v) 3/8
      (vi) 3/4
    The correct matching of the List I from the List II is

    A) A-(ii)      B-(iii)     C-(vi)     D-(i)

    B) A-(iv)     B-(v)      C-(vi)     D-(i)

    C) A-(iv)     B-(ii)      C-(vi)     D-(i)

    D) A-(i)       B-(ii)      C-(iii)     D-(iv)

    Correct Answer: C

    Solution :

    (A) Given,\[P({{E}_{1}})=\frac{1}{4},\,\,P\left( \frac{{{E}_{1}}}{{{E}_{2}}} \right)=\frac{1}{4}\] and        \[P\left( \frac{{{E}_{2}}}{{{E}_{1}}} \right)=\frac{1}{2}\] \[\Rightarrow \]               \[\frac{P({{E}_{2}}\cap {{E}_{1}})}{P({{E}_{1}})}=\frac{1}{2}\] \[\Rightarrow \]               \[P({{E}_{2}}\cap {{E}_{1}})=\frac{1}{8}\] Also,      \[P\left( \frac{{{E}_{1}}}{{{E}_{2}}} \right)=\frac{1}{4}\] \[\Rightarrow \]               \[\frac{P({{E}_{1}}\cap {{E}_{2}})}{P({{E}_{2}})}=\frac{1}{4}\] \[\Rightarrow \]               \[\frac{1}{8P({{E}_{2}})}=\frac{1}{4}\]  \[\Rightarrow \]  \[P({{E}_{2}})=\frac{1}{2}\] (B)\[P({{E}_{1}}\cup {{E}_{2}})=P({{E}_{1}})+P({{E}_{2}})-P({{E}_{1}}\cap {{E}_{2}})\]                 \[=\frac{1}{4}+\frac{1}{2}-\frac{1}{8}=\frac{5}{8}\] (C)\[P\left( \frac{{{{\bar{E}}}_{1}}}{{{{\bar{E}}}_{2}}} \right)=\frac{P({{{\bar{E}}}_{1}}\cap {{{\bar{E}}}_{2}})}{P({{{\bar{E}}}_{2}})}\]                 \[=\frac{1-P({{E}_{1}}\cup {{E}_{2}})}{1-P({{E}_{2}})}=\frac{1-\frac{5}{8}}{1-\frac{1}{2}}\]                 \[=\frac{3}{4}\] (D)\[P\left( \frac{{{E}_{1}}}{{{E}_{2}}} \right)=\frac{P({{E}_{1}}\cap {{{\bar{E}}}_{2}})}{1-P({{\overline{E}}_{2}})}\]                 \[=\frac{\frac{1}{4}-\frac{1}{8}}{1-\frac{1}{2}}=\frac{\frac{1}{8}}{\frac{1}{2}}=\frac{1}{4}\]


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