All About Pie Charts! 🥧
Let's learn about this tasty-sounding way to look at data!
What is a Pie Chart?
A **pie chart** (or a circle graph) is like a pizza that's been cut into slices. The whole pizza represents a **total amount**, and each slice shows a **part** of that total. Bigger slices mean bigger parts, and smaller slices mean smaller parts. It helps us see how different parts compare to each other and to the whole thing.
How to Draw a Pie Chart (The Math Part!)
To draw a pie chart accurately, we need to turn our data into fractions and then into angles. A full circle has **360 degrees (360°)**.
- Find the Total: Add up all the values. For our example, the total is 24 hours.
- Find the Fraction: For each part, make a fraction of the whole. (e.g., Sleep is 8 hours out of 24, so the fraction is 8/24).
- Calculate the Angle: Multiply each fraction by 360°. This tells you how big to make each slice. (e.g., For Sleep: (8/24) * 360° = 120°).
Try These!
1. Find the fraction of the circle for each piece of information.
Girls or Boys
Transport to school
Love/Hate Mathematics
2. Answer the questions based on the TV viewers pie chart.
(i) Which type of programmes are viewed the most?
(ii) Which two types of programmes have number of viewers equal to those watching sports channels?
Let's Draw a Pie Chart! (Ice Cream Flavours)
The favourite flavours of ice-creams for students of a school is given in percentages. Let's represent this data in a pie chart!
Step 1: Calculate the Angles
First, we convert percentages into fractions, and then into angles. A full circle is 360°.
| Flavours | Percentage | In Fractions | Fraction of 360° (Angle) |
|---|---|---|---|
| Chocolate | 50% | 50100 = 12 |
12 × 360° = 180° |
| Vanilla | 25% | 25100 = 14 |
14 × 360° = 90° |
| Other flavours | 25% | 25100 = 14 |
14 × 360° = 90° |
Step 2: Draw the Pie Chart
- Draw a circle with any radius you like. Mark its centre (O) and draw a starting line (radius OA).
- Draw the first sector. The angle for Chocolate is 180°. Use a protractor to measure and draw this angle from the line OA. This creates the first slice!
- Draw the next sectors. From your new line (OB), measure the next angle (90° for Vanilla) and draw it. The last section will be what's left over.
- Label your chart. Don't forget to write the name of the flavour in each slice.
Example: Family Expenditure
This pie chart gives the expenditure (in percentage) on various items and savings of a family during a month. Let's answer some questions about it!
(i) On which item, the expenditure was maximum?
(ii) Expenditure on which item is equal to the total savings of the family?
(iii) If the monthly savings of the family is ₹ 3000, what is the monthly expenditure on clothes?
Example 2: Baker's Shop Sales
On a particular day, the sales (in rupees) of different items of a baker's shop are given. Let's find the central angle of each sector.
| Item | Sales (in ₹) |
|---|---|
| ordinary bread | 320 |
| fruit bread | 80 |
| cakes and pastries | 160 |
| biscuits | 120 |
| others | 40 |
| Total | 720 |
Here the total sale is ₹ 720. Now, let's calculate the fraction and central angle for each item. Fill in your answers below!
| Item | Sales | In Fraction | Central Angle |
|---|---|---|---|
| Ordinary Bread | 320 | ° | |
| Biscuits | 120 | ° | |
| Cakes and pastries | 160 | ° | |
| Fruit Bread | 80 | ° | |
| Others | 40 | ° | |