Instructional Video10:11
Khan Academy

Permutations

10th - 12th
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...
Instructional Video10:16
Khan Academy

Combinations

10th - 12th
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.