New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    6 Boys and 5 Girls sat in a row randomly. What is the

    probability that no 2 Girls are together?
    A 1/22 Correct Answer Incorrect Answer
    B 1/11 Correct Answer Incorrect Answer
    C 2/11 Correct Answer Incorrect Answer
    D 2/21 Correct Answer Incorrect Answer
    E 1/21 Correct Answer Incorrect Answer

    Solution

    6 Boys and 5 Girls, i.e., a total of 11 people can be arranged in 11!/6!5! ways or, 462 ways.

    For no 2 Girls to sit together, arrangement can be done in the following way: [B are Boys]

    _ B _ B _ B _ B _ B _B_

    There are 7 spaces that can be taken up by 5 Girls so that no 2 of them sit together.

    Number of ways =  7 C 5  = 21.

    Required probability = 21/462 = 1/22

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