# Permutations and Combinations

- A permutation is a particular sequence of a given set of objects. A combination is the set itself without reference to order.

- The number of different permutations of
*n*distinct objects taken*r*at a time is

- The number of different combinations of
*n*distinct objects taken*r*at a time is- The number of different combinations of

- The number of different permutations of n objects taken n at a time, given that
*n*are of type_{i}*i*, where*i*= 1, 2,...,*k*and*Σn*=_{i}*n*, is- The number of different permutations of n objects taken n at a time, given that

- The number of different permutations of

**See also: **Probability.

**Subjects: ** Mathematics