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JEE Main & Advanced Mathematics Permutations and Combinations Question Bank Definition of combinations, Conditional combinations, Division into groups, Derangements

  • question_answer
    Everybody in a room shakes hand with everybody else. The total number of hand shakes is 66. The total number of persons in the room is  [MNR 1991; Kurukshetra CEE 1998; Kerala (Engg.) 2001]

    A) 11

    B) 12

    C) 13

    D) 14

    Correct Answer: B

    Solution :

     \[^{n}{{C}_{2}}=66\Rightarrow n(n-1)=132\Rightarrow n=12\].


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