Fundamental Counting Principle
The fundamental counting principle states that if there are ways to do one thing, and ways to do another thing, then there are ways to do both things.
Suppose you have shirts (call them , , and ), and pairs of pants (call them , , , and ). Then you have
Suppose you roll a -sided die and draw a card from a deck of cards. There are possible outcomes on the die, and possible outcomes from the deck of cards. So, there are a total of
possible outcomes of the experiment.
The counting principle can be extended to situations where you have more than choices. For instance, if there are ways to do one thing, ways to a second thing, and ways to do a third thing, then there are ways to do all three things.