JEE Main & Advanced Mathematics Permutations and Combinations Question Bank Self Evaluation Test - Permutations and Combinatioins

  • question_answer
    There are 10 points in a plane, no three are collinear, except 4 which are collinear. All points are joined. Let L be the number of different straight lines and T be the number of different triangles, then

    A) \[T=120\]

    B) \[L=40\]

    C) \[T=3L-5\]

    D) None of these

    Correct Answer: B

    Solution :

    [b] \[L{{=}^{10}}{{C}_{2}}{{-}^{4}}{{C}_{2}}+1=45-6+1=40\] \[T{{=}^{10}}{{C}_{3}}{{-}^{4}}{{C}_{3}}=120-4=3L-4\]

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