Notes on Pie Charts

What is a Pie Chart?

A Pie Chart is a circular graph that represents data as slices of a pie. Each slice shows a part of the whole, and the size of each slice is proportional to the quantity it represents.

Key Features of a Pie Chart

• It is a circle divided into sections.
• Each section represents a category of data.
• The size of each section depends on the percentage or fraction of the total data.
• The whole pie represents 100% of the data.

Steps to Create a Pie Chart

1. Collect Data: List the categories and their values.
2. Find the Total: Add up all the values.
3. Calculate the Angle for Each Section:

• Use the formula:
  $$
  \text{Angle} = \left(\frac{\text{Category Value}}{\text{Total Value}}\right) \times 360^\circ
  $$

1. Draw a Circle: This is the base of your pie chart.
2. Divide the Circle: Use the calculated angles to draw slices.
3. Label the Sections: Write the category names and percentages.

Example

Imagine you surveyed 50 students about their favorite fruits. The results are:

• Apples: 10 students
• Bananas: 15 students
• Oranges: 20 students
• Grapes: 5 students

Calculating the Angles

Total students:
$$
10 + 15 + 20 + 5 = 50
$$

Now, calculate each category’s angle:

• Apples:
  $$
  \frac{10}{50} \times 360 = 72^\circ
  $$
• Bananas:
  $$
  \frac{15}{50} \times 360 = 108^\circ
  $$
• Oranges:
  $$
  \frac{20}{50} \times 360 = 144^\circ
  $$]
• Grapes:
  $$
  \frac{5}{50} \times 360 = 36^\circ
  $$

Now, draw the pie chart and label each section accordingly!

Uses of Pie Charts

• Representing survey results
• Showing percentages in business reports
• Comparing proportions in real-life data

Things to Remember

✅ A pie chart always adds up to 100% $$(or (360^\circ))$$
✅ It is best used when comparing parts of a whole
✅ Too many categories can make it hard to read.