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 184-185 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.