RAJASTHAN ­ PET Rajasthan PET Solved Paper-2003

  • question_answer
    A hits an aim four times out of 5 trials, B hits three times out of 4 trials and C hits two times out of 3 trials. The probability that only two hits the target is

    A)  \[\frac{5}{12}\]

    B)  \[\frac{5}{6}\]

    C)  \[\frac{25}{60}\]

    D)  \[\frac{26}{60}\]

    Correct Answer: D

    Solution :

     Probability that A hits the aim, \[P(\overline{A})=\frac{4}{5}\] Probability that A does not hit the aim, \[P(B)=\frac{3}{4}\] Probability that B hits the aim \[P(B)=\frac{3}{4}\] Probability that B does not hit the aim, \[P(\overline{B})=\frac{1}{4}\] Probability that C hits the aim,\[P(C)=\frac{2}{3}\] Probability that C does not hit the aim\[P(\overline{C})=\frac{1}{3}\] \[\therefore \]Required probability \[=P(A\cap B\cap \overline{C})+(\overline{A}\cap B\cap C)+P(A\cap \overline{B}\cap C)\] \[=P(A)P(B)P(\overline{C})+P(\overline{A})P(B)P(C)+P(A)P(\overline{B})P(C)\] \[=\frac{4}{5}.\frac{3}{4}.\frac{1}{3}+\frac{1}{5}.\frac{3}{4}.\frac{2}{3}+\frac{4}{5}.\frac{1}{4}.\frac{2}{3}\] \[=\frac{12+6+8}{60}=\frac{26}{60}\]


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