Math Fundamentals18 sections · 814 units
Open in Course

Section Recap

What we learned

You learned the two fundamental counting rules:

1.1. Sum rule: Add when choices are mutually exclusive (OR)

2.2. Product rule: Multiply when choices are independent (AND)

You handled restrictions with complementary counting (total minus invalid). You used the pigeonhole principle to prove existence. You corrected overlaps with inclusion-exclusion.

You counted passwords, paths on grids, and letter combinations. These principles are the foundation for all combinatorics. Next: permutations and combinations.