**Probability**

**The Counting Principle**

The **Fundamental Counting
Principle** offers another way of calculating how many possible
outcomes of an event.

If there
are two or more variables (stages of activity) the total number of possible
outcomes is the **product** of the **number of possible outcomes** for **each
stage** of the activity.

Example: A clothing store sells shirts in eight different
sizes. For each size, there is a choice
of five different colors and for each color; there is a choice of six different
patterns. If the store has one of each
available type of shirt, how many different shirts does the store have?

In the above example there are three variables or stages so
I would multiply the 8 choices of sizes by the 5 colors and then the 6 patterns
to determine that there are 240 possible outcomes or different shirts.

If I then wanted to know the number of size 6, pink or blue,
stripes= 1 ∙ 2 ∙ 1 favorable
outcomes so the P(size 6, pink or blue, stripes) = _{}