To solve problems where the solution symbolizes a number of
possible combinations i.e. outcomes, we can use a tree-diagram.
Example:
Planet Bollywood offers chicken (C), beef (B) or vegetables (V)
served with either French fries (F) or mashed potatoes (M). How
many possible dinner alternatives or possible outcomes are there at
Planet Bollywood.
We draw a tree-diagram

The total number of possible outcomes are 6, 3 ∙ 2 = 6. This
principle is called the fundamental counting principle and the rule
is as follows.
If event x (in this case the chicken, the beef and the
vegetables) can occur in x ways. And event y (in this case French
fries or mashed potatoes) can occur in y ways. The x followed by y
can occur in x ∙ y ways.
Video lesson: How many outcomes are possible
when a die is rolled three times?