How do you find probabilities of compound events?

1 Answer
Nov 18, 2017

Answer:

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#