2. Questions Bank
  3. JEE Main & Advanced
  4. Mathematics
  5. Permutations and Combinations

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

  • question_answer
    If \[n\] and \[r\] are two positive integers such that \[n\ge r,\] then \[^{n}{{C}_{r-1}}\]\[+{{\,}^{n}}{{C}_{r}}=\]              [Kerala (Engg.) 2002]

    A) \[^{n}{{C}_{n-r}}\]

    B) \[^{n}{{C}_{r}}\]

    C) \[^{n-1}{{C}_{r}}\]

    D) \[^{n+1}{{C}_{r}}\]

    Correct Answer: D

    Solution :

      \[^{n}{{C}_{r-1}}\,+{{\,}^{n}}{{C}_{r}}\,={{\,}^{n+1}}{{C}_{r}}\] is a standard formula.


You need to login to perform this action.
You will be redirected in 3 sec spinner