Pie charts
In a nutshell
A pie chart shows things as proportions. Everything in a pie chart adds up to 360°and can be written in degrees, as a fraction or as a percentage.
Interpreting pie charts
Being able to convert between angles and proportions is important when making sense of a pie chart. The following formula can help and your answer can be calculated as a fraction or a percentage:
360angle=totalfrequency
Example 1
This pie chart represents the colour of different flowers growing in a field. In total there are 500 flowers; how many pink flowers are there?
Using the formula:
3605436054=500frequency=15%
Work out 15% of 500:
10%+5%=50+25=75
There are 75 pink flowers.
Drawing a pie chart
Drawing a pie chart involves working out each quantity as a proportion of 360 and hence an angle.
procedure
1. | Add all the values to find the total represented by the pie chart. |
2. | Find the number you multiply the total by to get 360. |
3. | Multiply each number by the multiplier to find the angle. |
4. | Draw using a protractor and label. |
Example 2
Draw a pie chart that represents the different instruments played by students in school.
Instrument | Trumpet | Piano | Guitar | Violin |
Number of players | 4
| 20
| 8
| 8 |
Find the total number of players:
4+20+8+8=40
Find the multiplier:
360÷40=9
Multiply every number by 40 to get the angle:
Instrument
| Trumpet
| Piano
| Guitar
| Violin
|
Angle
| 4×9=36° | 20×9=180° | 8×9=72° | 8×9=72° |
Draw and label: