1.3.3 Drawing a pie chart
You can use the fact that the sum of angles at a point is 360° to draw a pie chart.
Over a five-year period a mathematics tutor found that 16 of her students gained distinctions, 32 gained pass grades and 12 failed to complete the course. Draw a pie chart to represent these data.
First, calculate how many students there were altogether:
16 + 32 + 12 = 60 students.
The whole pie chart (360°) must, therefore, represent 60 students. This means that each student is represented by 360° ÷ 60 = 6°. So the angles for the three slices are
|distinctions||16 × 6 = 96°|
|pass grades||32 × 6 = 192°|
|failed to complete||12 × 6 = 72°|
The pie chart can be constructed by carefully measuring these angles at the centre of a circle. The slices should be labelled, and an appropriate title given to the chart. The source of the data should also be stated.