 # 12.06 Pie charts

Lesson

## Ideas

Can you identify and  compare fractions  of a circle?

### Examples

#### Example 1

a

Complete the statement:

A half is one whole which has been divided into equal parts.

Worked Solution
Create a strategy

Use the table below to help:

Apply the idea

A half is one whole which has been divided into 2 equal parts.

b

Which of the following represents \dfrac{1}{2} on a circle?

A
B
Worked Solution
Create a strategy

The bottom number (denominator) tells us the number of equal parts the shape has been broken into. The top number (numerator) tells us the number of parts we have shaded.

Apply the idea

The fraction \dfrac{1}{2} is asking for 1 out of 2 parts to be shaded. So the correct answer is Option B.

Idea summary

The following table shows how many parts are in a whole:

## Pie charts

This video looks at the features of a pie chart including the key/legend. Understanding these key features can help us to interpret the data.

### Examples

#### Example 2

Every student in Year 8 was surveyed on their favourite subject, and the results are displayed in this pie chart:

a

Which was the most popular subject?

Worked Solution
Create a strategy

Use the key to find the subject that is represented by the colour with the biggest part.

Apply the idea

We can see from the pie chart that the biggest part has the same colour as Maths in the key.

Maths was the most popular subject.

b

Which was the second most popular subject?

Worked Solution
Create a strategy

Use the key to find the subject that is represented by the colour with the second biggest part.

Apply the idea

We can see from the pie chart that the second biggest part has the same colour as History in the key.

History was the second most popular subject.

c

What percentage of the class selected Science, Phys. Ed., or Languages?

A
3\%
B
30\%
C
25\%
D
50\%
Worked Solution
Create a strategy

Find how much of the pie chart do the given subjects take up all together.

Apply the idea

The pie chart shows that the three subjects take up one quarter of the pie chart, and one quarter is equal to 25\%.

Idea summary

The key tells us what each segment of the pie chart represents. When we don't need to know exact numbers, a pie chart is a great way to see how data is spread.

### Outcomes

#### MA3-18SP

uses appropriate methods to collect data and constructs, interprets and evaluates data displays, including dot plots, line graphs and two-way tables