# What is a pie chart?

## What is a pie chart?

**Pie charts** are used in data handling and are **circular charts divided up into segments which each represent a value.**

**Pie charts are divided into sections (or 'slices') to represent values of different sizes. **For example, in this pie chart, the circle represents a whole class. Each member of the class was asked what their favourite subject was, so each segment of the circle represents a different favourite subject:

Pie charts are a **visual device to help us understand data more easily**. For example, in this pie chart we can see that sport was the most popular subject as more than half of the class said it was their favourite subject.

## Pie charts and percentages and angles

**Pie charts often label each segment with a percentage**, so it is vital that children understand percentages before they can properly interpret pie charts.

For example: a pie chart showing the favourite fruit of children in one class, may have 3 segments, showing strawberries as 55%, bananas as 39% and blueberries without a percentage. Children would need to work out the percentage of children who liked blueberries by taking 55% and 39% away from 100. The remaining number (6) would be the missing percentage.

**Children would also need to know that if a quarter of the pie chart is clearly marked, this represents 25%. If half the pie chart is clearly marked, this represents 50%.**

Children in Year 6 will sometimes be given a question on a pie chart that relies on their knowledge of angles, for example:

In order to answer questions about this pie chart they would need to know that the data about Tony is shown on a right-angled section which therefore means it represents 25% or a quarter of the information given. Kaias's section is half or 50% of the data. If James represents 5% then Hugo must represent 20%.

In Year 6, **children will learn how to construct pie charts**. For example: they may be asked to represent 'half' on a pie chart by drawing a vertical or horizontal line across its centre. They may be asked to represent 'a quarter' by using a protractor to measure an angle of 90° and then draw a line segmenting this off.

More able children may be asked to relate their knowledge of percentages to their knowledge of angles. For example, to represent 30% on a pie chart, they would need to work out what 30% of a full turn (360°) is. They would then need to measure this angle on the pie chart with their protractor (108°), draw a line and then label the segment correctly.