2. Solved Papers
  3. CEE Kerala Engineering

CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2004

  • question_answer
    \[^{n}{{p}_{r}}=3024\]and\[^{n}{{C}_{r}}=126\],then r is:

    A)  5                                            

    B)  4

    C)  3                            

    D)  2

    E)  1

    Correct Answer: B

    Solution :

    Given, \[^{n}{{P}_{r}}\,=3024\] \[\therefore \]  \[\frac{n!}{(n-r)!}=3024\] and      \[^{n}{{C}_{r}}=\frac{n!}{r!(n-r)!}\] \[\Rightarrow \]               \[126=\frac{3024}{r!}\] \[\Rightarrow \]               \[r!=24=4!\] \[\Rightarrow \]               \[r=4\]


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