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Fast Counting (The Counting Principle)

Let's figure something out:

You're planning a date:  dinner, entertainment and dessert. 

You have two choices for dinner, Happy Meals at McDonald's and microwave burritos at the local Quickymart. 

You have three choices for entertainment:  bowling, a movie or watching wrestling on TV. 

You have two choices for dessert:  s'mores and pie.  How many possible dates are there?

When in doubt, make a chart.  (This is called a tree diagram.)

First, we pick the meal ... date --> 1 ) McD or 2 ) QM


Next, we pick the entertainment... ... date --> 1 ) McD or 2 ) QM --> 1 ) B or 2 ) M or 3 ) WWE
 

Finally, we pick the dessert...

date --> 1 ) McD or 2 ) QM --> 1 ) B or 2 ) M or 3 ) WWE --> 1 ) S or 2 ) P
 

Every possible date is represented here.  You can trail through and find

McDonald's, movie, s'mores

Quickymart, WWE, pie

and so on.

To count how many total possible dates there are, we just count the tips of the last branches.

There are 12 possible dates.