Intermediate Counting and Probability advances beyond basic combinatorics to cover techniques such as the Principle of Inclusion-Exclusion, generating functions, and recursion for math competitions and advanced study. Key strategies include developing intuition through problem-solving before reading solutions, constructing one-to-one correspondences, and applying Pigeonhole Principle. Explore the Art of Problem Solving's comprehensive curriculum at Art of Problem Solving . Scholars Math 9.1: Intermediate Counting & Probability