Core idea
Events may be mutually exclusive or exhaustive. Use P(Aᶜ)=1−P(A), P(A∪B)=P(A)+P(B)−P(A∩B); define the sample space and check 0≤P(A)≤1.
Worked check
A fair die gives P(even)=3/6=1/2.
Practice
- Show each step and state any domain or assumption.
- Check the result by substitution, estimation or a second method.