Unit 8: Combinatorics
In this unit, you will learn to count. That is, you will learn to classify the objects of a set in such a way that one of several principles applies.
Completing this unit should take you approximately 11 hours.
8.1: Counting Problems as Sampling Problems with Conditions on the Structure of the Sample
8.2: The Inclusion-Exclusion Principle
8.2.1: The Case with Just Two Sets
8.2.2: The Proof
8.2.3: Other Examples
8.3: The Pigeon-Hole Principle (PHP)
8.3.1: The Standard Principle
8.3.2: Using the PHP Idea in Other Settings