JCECE Engineering JCECE Engineering Solved Paper-2011

  • question_answer
    Three numbers are chosen from \[1\] to\[30\]. Find the probability that they are not consecutive.

    A) \[\frac{16}{81}\]                                              

    B) \[\frac{144}{145}\]

    C) \[\frac{80}{145}\]                                            

    D) \[\frac{65}{81}\]

    Correct Answer: B

    Solution :

    The total number of ways in which \[3\] numbers can be chosen out of \[30\] numbers\[{{=}^{30}}{{C}_{3}}=4060\].  The number of ways of choosing \[3\] consecutive numbers is\[28\]. Therefore, the number of ways in which the three numbers chosen are not consecutive is\[4060-28=4032\]. Hence, the required probability\[=\frac{4032}{4060}=\frac{144}{145}\]


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