Constructing and Interpreting Pie Charts

1. 1 Display a frequency table of favourite sports in a class of 30. 'We want to see the proportions at a glance. A pie chart shows each category as a slice — the bigger the slice, the bigger the proportion.'
2. 2 Each degree = 1/360 of the whole circle. Formula: angle = (frequency ÷ total) × 360. For football: 12/30 × 360 = 144°. Students calculate all sector angles. Check: all angles must sum to 360°.
3. 3 Draw a circle. Mark the centre. Draw the first radius. Measure 144° with the protractor, draw the second radius. Label the sector. Repeat for each sector, starting each new sector from the last radius drawn.
4. 4 Students colour each sector, add a title, and create a legend. Review: 'Does it look right? Is the largest sector the most popular sport?'
5. 5 Display a pre-made pie chart. 'Which category is most popular?' (Largest sector.) 'Approximately what fraction of people chose...?' Students estimate fractions from visual inspection before calculating from given angles.
6. 6 Given a pie chart with angles and a total of 60 people, calculate the frequency for each sector. Frequency = (angle ÷ 360) × total. Apply to three sectors.
7. 7 Two pie charts from different schools. 'Can you compare the actual number of students who chose football?' (No — only proportions, not raw numbers, are shown.) Discuss the limitation of pie charts.

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