Hi, what do you want to do?
Khan Academy
Permutations
This video is an introduction to permutations. Sal shows two examples, defines the mathematical notation for permutations, and derives a formula for finding a permutation without repetition of choices. He tries to convey an intuitive...
Khan Academy
Combinations
How many different ways can five people be arranged in any order in three chairs? Sal shows how combinations are different than permutations. He derives the formula for finding the combination without repetition.