Sometimes, putting dependent events on a probability tree diagram is not appropriate. In this case, a Venn diagram can illustrate the information more clearly. Read in your textbook to see how a Venn diagram is used to solve a probability problem.
Recall from Unit 1 that the Textbook uses the notation A \ B which is read A minus B . It denotes the set of elements that are in set A but not in set B . It is the red region in each Venn diagram below.



A
\
B
when
B
A

A
\
B
when they are disjoint

A
\
B
when they intersect


Read pages 184185 Example 2 in your textbook, Principles of Mathematics 12 . Complete the Your Turn question on page 185 for more practice related to dependent events. Click here to verify your answer . 
In textbook Example 2, the probability formula for dependent events is rearranged as follows.
This formula is used to find the probability of an event given the occurrence of a previous event . It is used when the intersection of A and B is known or can be found using a Venn diagram.