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

  • question_answer
    Four boys and three girls stand in a queue for an interview, probability that they will in alternate position is                    [UPSEAT 2001]

    A)            \[\frac{1}{34}\]                       

    B)            \[\frac{1}{35}\]

    C)            \[\frac{1}{17}\]                       

    D)            \[\frac{1}{68}\]

    Correct Answer: B

    Solution :

                       Four boys can be arranged in \[4\,!\] ways and three girls can be arranged in 3! ways.                    \[\therefore \]  The favourable cases \[=4\,!\,\times \,3\,!\]                    Hence the required probability \[\frac{=4\,!\,\times 3\,!}{7\,!}=\frac{6}{7\times 6\times 5}=\frac{1}{35}\].


You need to login to perform this action.
You will be redirected in 3 sec spinner