Venn Diagram

You can use a venn diagram to show frequencies in a probability question
This venn diagram shows the results when 50 people were asked whether they owned a dog or a cat
The rectangle represents everyone who was surveyed
The number in each section tells you how many people that section represents
Some people owned a dog and a cat so the ovals overlap * The overlap can be represented by D n C

* 21+18+5 = 44 people owned a dog or a cat, you can write this as D u C