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.
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:
Draw a pie chart to represent this information.
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:
|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:
In this section you have learned about how to present data in pie charts.