# Probabilities of single events

**Calculating probability**

The following formula can be used to find the probability of an **outcomes** where two events are **equally likely**:

Example 1

If a bag contains 10 marbles, of which 1 is yellow, 3 is green, 4 is blue and 2 are red marbles. What is the probability of pulling a blue marble?

**Calculating probabilities**

If the probability of an event occurring is *p *then the probability of an event not occurring is 1 – *p*

Example 2

What would be the probability of not pulling out a blue marble?

The probability of pulling out a blue marble is 0.4

Therefore 1 – 0.4 = 0.6