Formulae
1. Factorial Notation - Let n be a positive integer. Then, factorial n denoted n! is defined as:
n! = n(n - 1)(n - 2) ... 3.2.1.
2. Number of Permutations - Number of all permutations of n things, taken r at a time, is given by:
nPr = n(n - 1)(n - 2) ... (n - r + 1) = n!/(n - r)!
3. Then, the number of permutations of these n objects is = n!/(p1!).(p2)!.....(pr!)
4. Number of Combinations - The number of all combinations of n things, taken r at a time is:
nCr = n!/(r!)(n - r)! = n(n - 1)(n - 2) ... to r factors/r!
Exercise : Permutation and Combination MCQ Questions and Answers
Questions will be uploaded soon.