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Everyday maths 1
Everyday maths 1

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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.

Case study _unit4.4.1 Example: Soap operas

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

Download this video clip.Video player: 17_ani_pie_charts.mp4
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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 _unit4.4.1 Activity 8: Creating a pie chart

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

Table _unit4.4.1
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:

Table _unit4.4.2
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:

Described image
Figure _unit4.4.1 Figure 8 Pets pie chart

Summary

In this section you have learned about how to present data in pie charts.