When we are drawing a pie chart, we will normally be given a frequency table and have to link the frequencies to the angles we are going to draw.

**Example:**

Here are the makes of some cars.

Draw a pie chart to show this data.

Make | Ford | Nissan | BMW | Mini | Vauxhall |

Frequency | 4 | 5 | 2 | 3 | 6 |

**Step 1: Find out what the total frequency is.**

If we add the frequencies together, we get 4 + 5 + 2 + 3 + 6 = 20

This means that our pie chart has to represent 20 cars in total.

**Step 2: Work out what each car is worth as an angle.**

All circles add up to 360°. If we split this into 20 parts:

360 ÷ 20 = 18°

**Step 3: Work out what each category is worth.**

There are four Fords and each one is worth 18°. This means the Ford category is worth 4 x 18 = 72°

We can do this for all the other categories:

Make | Ford | Nissan | BMW | Mini | Vauxhall |

Frequency | 4 | 5 | 2 | 3 | 6 |

Angle | 72 | 90 | 36 | 54 | 108 |

We can now check we have done this correctly by adding up all the angles. We should always get 360.

**Step 4: Draw the angles onto a pie chart and label the sectors.**

You can either give a key, or write the names in the sectors. It doesn't matter which you do, you'll still get the same marks either way.

Let's move on to some questions now.