Addition Rule (Probability "or") (Jump to: Lecture | Video )

When flipping a coin, the two events (heads and tails) are mutually exclusive.

Figure 1.

What is the probability of flipping a coin and getting heads or tails?

Figure 2.

There is a 100% chance the coin will land on either heads or tails.

When picking randomly from a deck of cards, the two events heart and king are not mutually exclusive.

Figure 3.

When picking randomly from a deck of cards, what is the probability of choosing a card that is a heart or a king, but not both?

Figure 4.

The probability of drawing a card that is either a heart or a king, but not both, is approximately 31%.