How do you work out the probability of an event occuring?

Probability of an event occurring is

the number of wanted outcomes divided by the total number of outcomes.

Probabilities are expressed as decimals or fractions between 0 and 1

You will form a fraction. The top or numerator of the fraction will be the number of ways that the specified event can happen. The bottom or denominator of the fraction will be the number of all the possible events in the situation.

You can work out the probability of an event by creating a fraction e.g. 1/4 means there is a 1 in 4 chance that a specific event will occur out of all possible events. This can also be expressed as a decimal e.g. 0.25 or a percentage e.g. 25%.