JEE Main & Advanced Mathematics Probability Question Bank Use of permutations and combinations in probability

  • question_answer
    Six boys and six girls sit in a row randomly. The probability that the six girls sit together

    A)            \[\frac{1}{77}\]                       

    B)            \[\frac{1}{132}\]

    C)            \[\frac{1}{231}\]                     

    D)            None of these

    Correct Answer: B

    Solution :

                       6 boys and 6 girls can be arranged in a row in \[12\,\,!\] ways. If all the 6 girls are together, then the number of arrangement are \[7\,\,!\,\times \,6\,\,!\].                    Hence required probability\[=\frac{7\,\,!\,.\,6\,\,!}{12\,\,!}\]                                                           \[=\frac{6\times 5\times 4\times 3\times 2}{12\times 11\times 10\times 9\times 8}=\frac{1}{132}\].


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