Abacus

Counting

You may be surprised to find that we're going to study something so basic as counting. But it's core to probability, and it's not quite that basic. In fact there's enough to it that it even has a fancy name, which is combinatorics. We'll just call it counting though.

First we'll learn a few important principles of counting. Then we'll learn about permutations and combinations, which give us useful formulas for counting things.