A SYSTEMATIC APPROACH TO PERMUTATIONS AND …

Permutations are ordered arrangements: there are more of them because ABC, ACB, BAC, etc. are considered different. For example, a 'trifecta' bet on a horse race (first 3 horses in correct order) is a permutation. Combinations are unordered selections: there are fewer of them because ABC, ACB, BAC, etc. are considered the same. ................
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