Pie Charts — Revision Notes

⚡ 30-Second Revision

Revision checked 17 October 2026.

Whole = 100% = 360°.
Amount = own total × own share.
Smaller share can mean larger amount.
Combine amounts before calculating a combined share.
Percentage points are not relative percent change.

2-Minute Revision

A 25-percent share of 800 is 200; a 20-percent share of 1,200 is 240. The amount rises although composition shifts away from the category. Across pies, preserve each total. To combine 40 percent of 200 and 20 percent of 300, add 80 and 60, then divide by 500 to get 28 percent. Do not average the percentages without weights.

5-Minute Revision

Original drill: A category occupies 72° of a 900-unit chart and 54° of a 1,200-unit chart. Both amounts are 180. Its share drops from 20 to 15 percent, a fall of 5 percentage points or 25 percent relative to the original share. Its amount does not fall. Now remove both totals: only the share comparison remains determined. This exercise isolates angle conversion, amount comparison and missing-information judgement.

Vyyuha Quick Recall

WHOLE: Which total; Harmonise units; Obtain amounts; Label the comparison; Examine overlap.