Year 8 Interactive Maths - Second Edition

## Pie Charts

Pie charts are useful to compare different parts of a whole amount.  They are often used to present financial information.  E.g. A company's expenditure can be shown to be the sum of its parts including different expense categories such as salaries, borrowing interest, taxation and general running costs (i.e. rent, electricity, heating etc).

A pie chart is a circular chart in which the circle is divided into sectors.  Each sector visually represents an item in a data set to match the amount of the item as a percentage or fraction of the total data set.

#### Example 9

A family's weekly expenditure on its house mortgage, food and fuel is as follows:

Draw a pie chart to display the information.

##### Solution:

We can find what percentage of the total expenditure each item equals.

Percentage of weekly expenditure on:

To draw a pie chart, divide the circle into 100 percentage parts.  Then allocate the number of percentage parts required for each item.

###### Note:
• It is simple to read a pie chart.  Just look at the required sector representing an item (or category) and read off the value.  For example, the weekly expenditure of the family on food is 37.5% of the total expenditure measured.
• A pie chart is used to compare the different parts that make up a whole amount.