Principles of Counting & Combinatorics

Choose counting methods by defining what makes two outcomes different. Practice sum and product rules, permutations, combinations, repeated letters, circular seating, labeled and unlabeled groups, stars and bars, and constrained arrangements. Prerequisites: basic algebra, sets and elementary probability rules. Worked solutions move from direct enumeration to complements, blocks, occupancy shifts and justified symmetry factors. Each explanation identifies the overcount or omitted restriction behind the distractors.

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