Diagrammatic Representation of Data — Pie Diagrams

A pie diagram (or pie chart) represents the different components of a total by the sectors of a circle, with the angle of each sector kept proportional to that component's share of the whole. Since a full circle measures $360^\circ$, the angle for any component is obtained as:

Steps to construct a pie diagram:

1. Express each component as a proportion (or percentage) of the total.
2. Convert each proportion into a sector angle using the formula above.
3. Draw a circle of any convenient radius, and mark off sectors of the calculated angles using a protractor, usually starting from the 12 o'clock position and moving clockwise.
4. Shade or label each sector, generally in decreasing order of size, for easy reading.

Illustration. Suppose a family's total monthly spending of ₹40,000 is divided as: food ₹16,000, rent ₹8,000, education ₹6,000, savings ₹6,000, and other items ₹4,000. As a share of the total, each component's angle works out as $\frac{16000}{40000}\times360^\circ = 144^\circ$ for food, $\frac{8000}{40000}\times360^\circ = 72^\circ$ for rent, $\frac{6000}{40000}\times360^\circ = 54^\circ$ each for education and savings, and $\frac{4000}{40000}\times360^\circ = 36^\circ$ for other items. As a check, all five angles must add up to exactly $360^\circ$: $144+72+54+54+36 = 360^\circ$. …