When two events occur, there are several possible outcomes.

For example, when a coin is thrown, it can land heads up (H) or tails up (T).

So when two coins are thrown, the possible outcomes are:

H H

H T

T H

T T

There are four possible outcomes.

So the probability of getting two heads, P(HH) = 1/4

The probability of getting one head, P(H) = 2/4 = 1/2 because we can either have HT, or TH.

**Make carefully organised, systematic lists when determining all the outcomes. Do not just write out the outcomes randomly.**