Pie Charts

What Is a Pie Chart?

A pie chart is a circular graph used to show how data is split between different categories. Each slice or sector of the circle represents a part of the whole.

• The size of each sector depends on the proportion of the data it represents.
• The whole circle adds up to $360\degree$.
• Pie charts are great for showing percentages or fractions of a total.

How Do I Draw a Pie Chart?

Step-by-Step:

Suppose a class of 30 students were asked their favourite hobby:

Step 1: Find the Total

Total students = 12 + 6 + 8 + 4 = 30

Step 2: Turn Each Category Into a Fraction

Step 3: Multiply Each Fraction by $360\degree$ to Get Angles

Step 4: Draw the Pie Chart

Start with a circle and draw a vertical line from the center straight up.

Use a protractor to measure and draw each angle.

Label each slice with its category.

How Do I Use a Pie Chart?

Pie charts can be used to estimate values or solve problems involving proportions.

Example:

A pie chart shows how a café sells different drinks:

Coffee: $108\degree$

Tea: $72\degree$

Juice: $90\degree$

Water: $90\degree$

Let’s say $108\degree$ = 180 coffees sold.

How many drinks were sold altogether?

Step 1: Find What $1\degree$ Represents

If $108\degree$ = 180 coffees

Then $1\degree$ = $\frac{180}{108} = 1.67$ drinks (rounded)

Step 2: Multiply by 360

Total = $1.67 \times 360 \approx 600$ drinks

 
(b) How many juices were sold?

Juice is $90\degree$

So:

$90 \times 1.67 = 150$ juices

Example

At a local animal shelter, a pie chart shows the types of animals adopted in one month.

(a) If $120\degree$ represents 48 dogs, how many animals were adopted in total?

$1\degree$ = $\frac{48}{120} = 0.4$ animals

360° = $0.4 \times 360 = 144$ animals

(b) How many rabbits were adopted?

• Rabbits = $60\degree$
• $60 \times 0.4 = 24$ rabbits

Key Takeaways

• Pie charts show data as parts of a whole.
• Use fractions or ratios to convert data into angles.
• Total circle = $360\degree$
• Be careful with scale—sometimes pie charts are not to be measured.