# Counting Rules (Probability)

When you get introduced to the basics of probability, one of the first things you need to master is learning how to Count.

Addition Rule: If an experiment can be done in $n_{1}$ OR $n_{2}$ different ways, the total number of possibilities is $n_{1}+n_{2}$

Multiplication Rule: If an experiment A can be done in $n_{1}$ AND experiment B can be done in $n_{2}$ different ways, the total number of possibilities is $n_{1}×n_{2}$

$n_{k}$ rule: $k$ objects can be sampled with replacement from $n$ objects in $n_{k}$ total ways.

You should also be familiar with when to use Permutations vs. Combinations.

There is this really good playlist that I watched over the summer of 2022 teaching me how to count.

The next step are the Probability Rules.