CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2003

  • question_answer If\[^{n}{{C}_{3}}=220,\]then n equals to:

    A)  10                         

    B)         11

    C)  12                         

    D)         9

    E)  8

    Correct Answer: C

    Solution :

    \[^{n}{{C}_{3}}=220\] \[\Rightarrow \]               \[\frac{n!}{(n-3)!3!}=220\] \[\Rightarrow \]               \[n(n-1)(n-2)=220\times 6\] \[\Rightarrow \] \[n(n-1)(n-2)=12(12-1)(12-2)\] \[\Rightarrow \]               \[n=12\]

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