Mathematics - Probability - Compound Events - Permutations and combinations - Permutations and Combinations

10 steps: (1) PERMUTATION: arrangement where ORDER matters. (2) How many ways to arrange 3 books from 5? First position: 5 choices, second: 4, third: 3. Total: 5×4×3 = 60. (3) Formula: P(n,r) = n!/(n-r)!. P(5,3) = 5!/2! = 120/2 = 60. (4) Factorial: 5! = 5×4×3×2×1 = 120. (5) Special case: arrange ALL