Question

How do you find probabilities of compound events?

Answer 1

Depends on the relation between the events.

Explanation:

Example1: probability of rolling a 3 or a 5 with one throw.
`P(3)=1/6`, `P(5)=1/6`
Since this is an exclusive OR situation we ADD the probabilities:
`P(3or5)=P(3)+P(5)=1/6+1/6=1/3`

Example2: probability of first rolling a 3, and then a 5 with one die.
1st roll: `P(3)=1/6`, 2nd roll: `P(5)=1/6`
Since this is an AND situation, we MULTIPLY:
`P(3,5)=1/6xx1/6=1/36`
Note: if the question were about 'a 3 and a 5' (in any order) we'd have to add: `P(5,3)=1/36`