Combinations

A selection of distinct objects without regard to order is called a combination.

The number of \(r\) objects selected from \(n\) objects is denoted by \(_nC_r\) and is given by the formula

\[_nC_r=\frac{n!}{(n-r)!\cdot r!}\]

The key difference between permutations and combinations is:

Permutations-order matters

Combinations-order does NOT matter