We already encountered Venn Diagrams when we looked at set theory. Let’s practice counting the number of elements within Venn Diagrams (counting is an important skill in probability, as we often want to count the number of favourable outcomes and the total number of outcomes, to use our simple probability formula.

Exercise

Let’s complete exercise 7 from pages 300 and 301 of the core textbook:

The answers are below:

Now we are prepared to tackle probability problems using Venn Diagrams.

Example

(a) What is the probability that a randomly selected cat will like both food A and food B?

(b) What is the probability that a randomly selected cat will like only food A?

(c) What is the probability that a randomly selected cat does not like food B?

Exercise

Let’s complete exercise 8 from pages 303 and 304 of the core textbook:

The answers are below: