4 Pie charts

Charts are basically maths pictures. There are two types of charts: bar charts, which you’ll look at in the next section, and pie charts.

Pie charts are a clear way of presenting data, but they can be difficult to draw and the calculations involved in creating them can be complicated.

A pie chart is a circle (or ‘pie’) divided in sections (or ‘slices’). The sizes of these sections represent the data. Pie charts must contain both a title and a key that explains what each section means.

Example: Soap operas

How would you present information as a pie chart? Watch the following video to find out.

Transcript

Now try the following activity. If you get stuck, refer to the method summary above, and remember to check your answers once you have completed the questions.

Activity 8: Creating a pie chart

In a survey, 18 people were asked what their favourite pets were. The responses were as follows:

Pet	Frequency
Cat	5
Dog	6
Rabbit	4
Bird	1
Fish	2

Draw a pie chart to represent this information.

Answer

To find out how many degrees each animal is represented by, you must carry out this calculation:

• 360 ÷ 18 = 20

Therefore, each animal is represented by 20°. We can then calculate the size of each section:

Pet	Frequency	Angle
Cat	5	5 × 20° = 100°
Dog	6	6 × 20° = 120°
Rabbit	4	4 × 20° = 80°
Bird	1	1 × 20° = 20°
Fish	2	2 × 20° = 40°

From these measurements you should construct a pie chart as follows:

Figure 8 Pets pie chart