A pie chart's full circle always represents 360° or 100% — every sector's share of the whole comes from comparing its slice to that one fixed total.
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A bar graph compares separate categories; a line graph tracks how ONE thing changes over time.
📊 Sample data — books read by 5 students
| Student | Riya | Aman | Zara | Kabir | Ishaan |
|---|---|---|---|---|---|
| Books read | 12 | 8 | 15 | 10 | 5 |
Reading a bar graph: the tallest bar (Zara, 15 books) shows the highest value. The total across all five students is 12+8+15+10+5=50, so the average is 50÷5=10 books.
A pie chart splits a whole into slices — every slice's angle is a direct, fixed proportion of the full 360°.
📌 Working with a pie chart
The whole circle = 360° = 100%. A sector's share of the data = (its angle ÷ 360) × 100%.
To find the actual count from a percentage: multiply the total by that percentage.
Worked example: a sector of 90° in a class of 200 students represents 90÷360×100=25%, which is 200×0.25=50 students.
Trap: never assume all sectors are equal size just by looking — always calculate from the given angle or percentage.
Achievers questions often combine two different graph readings into one multi-step calculation.
Pro tip: always write down what the question gives you as raw numbers FIRST (angles, percentages, bar heights) before starting to calculate — this prevents mixing up degrees and percentages mid-problem.
12 questions on reading and interpreting bar graphs, line graphs and pie charts.
