Q.Data given in previous example (share of income from various sources for Indian central govt. for the year 2019-20; Goods & Services Tax 18%, Union Excise Duties 7%, Customs 4%, Income-Tax 17%, Corporate Tax 18%, Borrowings & Other Liabilities 20%, Non-Debt Capital Receipts 6%, Non-Tax Revenue 10%) can be represented through Pie Chart. Construct the pie chart, computing each component's share as a fraction of $360^{\circ}$ (e.g. $\dfrac{18}{100} \times 360^{\circ}$ for Goods & Services Tax).

Pie Chart – A First Look

Imagine you have a pizza. You want to share it with friends, and each person gets a slice. The whole pizza is one complete thing — your total data. Each slice is a part of that total. A pie chart is just that: a circle (the "pie") cut into slices, where each slice's size shows how big that part is compared to the whole.

The key idea is simple: the whole circle represents 100% of the data, and each slice represents a percentage of that total. The bigger the percentage, the bigger the slice.

---

The Intuition: Why a Circle?

Why not a bar or a line? Because a circle is the only shape where you can naturally see "parts of a whole." When you look at a bar chart, you compare heights. When you look at a pie chart, you compare angles — and angles are directly proportional to the quantity they represent.

If 50% of your friends like pepperoni, that slice takes up half the circle — an angle of $180^\circ$. If 25% like cheese, that's a quarter of the circle — $90^\circ$. The angle of each slice is the visual cue.

---

The Precise Statement

A pie chart (also called a circle graph) is a circular statistical graphic divided into sectors. Each sector corresponds to a category of data, and its central angle is proportional to the frequency (or percentage) of that category.

That's it. The whole circle is $360^\circ$, so each slice gets a fraction of that circle equal to its fraction of the total.

---

Step-by-Step Construction

Suppose you have data on how 30 students travel to school:

Step 1: Find each fraction of the total.

• Bus: $15/30 = 0.5$ (half)
• Car: $9/30 = 0.3$ (three-tenths)
• Walk: $6/30 = 0.2$ (one-fifth)

Step 2: Convert each fraction to an angle.

• Bus: $0.5 \times 360^\circ = 180^\circ$
• Car: $0.3 \times 360^\circ = 108^\circ$
• Walk: $0.2 \times 360^\circ = 72^\circ$

Check: $180 + 108 + 72 = 360^\circ$ — the circle is complete.

Step 3: Draw the circle and measure each angle from the centre. Label each slice with the category and its percentage (or number).

---

What to Read from a Pie Chart …