Probability: Permutations and Combinations

This video is a short primer on the concepts of permutations and combinations.

Both permutations and combinations count the ways that (r) objects can be taken from a group of (n) objects, but permutations are arrangements (sequence matters), while combinations are selections (order does not matter). For example, how many ways can you seat people at a table? That's permutation. How many poker hands are available in five-card draw? That's a combination.