Combinations

Probability · Axiom Academy

Counting selections when order doesn't matter 1. Combinations vs Permutations The key difference: in combinations, order doesn't matter. The selections A,B,C , B,A,C , and C,B,A are all the same combination. Watch how permutations collapse into combinations: The number of ways to choose r items from n items (without regard to order) is given by the combination formula. Let's see why we divide by r!: How many different 5-card poker hands can be dealt from a standard 52-card deck? Visualizing choosing 5 cards from 52: A classic application: forming a committee of 3 people from a group of 7. Watch the calculation step by step:

This is the written version of the interactive lesson above. See the full Probability course.