Pie Chart

• How pie charts show part-to-whole relationships using central angles and sector areas.
• To convert between degrees, percentages, and absolute values given the total.
• To compare sectors and solve "how much more" questions on budget and expenditure pies.
• To combine pie charts with tables when totals differ between groups.

Level 1 — Foundations

Verbal: A full circle = 360° = 100% of the whole. Each slice (sector) represents a category's share.

Conversion formulas:

Reading tips: Larger slice → larger share. Labels may show % directly or only category name — use protractor only if exam allows; usually angles are nice numbers (90°, 120°).

Multi-pie problems: Two pies with different totals — do not compare slice angles across pies for absolute amounts; compare percentages then multiply by respective totals.

Level 2 — Exam depth

Semi-pie / doughnut: Same math; missing slice may mean "other" or omitted category — read caption.

Exploded slice: Emphasis only; angle unchanged unless stated otherwise.

Reverse engineering total: If Food = ₹450 and angle = 90°, total = 450 × (360/90) = ₹1800.

Average sector: Mean of percents only equals meaningful "average category" if categories are equally weighted — usually not the same as average of values.

Combined with bar graph: Pie for composition, bar for trend over time — common two-chart DI sets in exams.

Find expenditure from angle and total budget

Monthly budget = ₹36,000. Rent sector = 120°.
Step 1 — Rent percent = 120/360 × 100 = 33⅓%.
Step 2 — Rent amount = (1/3) × 36,000 = **₹12,000**.
Step 3 — Check: remaining 240° = ₹24,000 ✓

Compare two categories from degrees

Transport = 72°, Education = 54° on same pie.
Difference in share = (72−54)/360 × 100 = 5%.
If total income ₹50,000, Transport exceeds Education by 5% of 50,000 = **₹2,500**.

• A sector is 90° — what percent and what fraction of the whole?
• Total 800 students; Sports 25% — how many students?
• Rent 110°, Food 130° — can remaining sectors include a 150° slice? Why?
• Stretch: Pie shows 2023 only; bar shows 2020–2023 trend — list two questions you can/cannot answer.

Revision tip: Revisit adjacent topics in Data Interpretation before mixed practice on Pie Chart.

Open the Practice tab for graded questions on Pie Chart.

Memorise the angle–percent table: 30°=8⅓%, 45°=12.5%, 60°=16⅔%, 90°=25%, 120°=33⅓%, 180°=50%. On compound questions, convert all sectors to amounts using the stated total before comparing across categories. If only two sector angles are given and the rest is "Other", subtract from 360° first. Check that sector percentages sum to 100% within rounding tolerance.