Percentage in Pie Charts

Learn to read pie charts and convert fractions to percentages!

1. Reading Pie Charts

A pie chart shows how a whole is divided into parts. All parts add up to 100%!

Example: Books borrowed by 4 classes

Total = 200 books

(a) How many books were borrowed by Class D?

200 − 60 − 20 − 70 = 50 books

(b) Which class borrowed the most books?

Class C (70 books = 35%)

(c) What percentage did Class B borrow?

$\frac{20}{200} \times 100\% =$ 10%

2. Percentages in Pie Charts

Pie charts often show percentages directly. Remember: all percentages must add up to 100%!

Example: Favourite sports of 40 students

Question: If 40 students were surveyed, how many chose Football?

Solution:

Football = 40% of 40 students

= $\frac{40}{100} \times 40$

= 16 students

3. Converting Fractions to Percentages

Sometimes pie charts show fractions. You can convert these to percentages!

Example: Favourite pets in a class

Hamster

$\frac{1}{4}$ = 25%

Rabbit

$\frac{1}{5}$ = 20%

Cat

? = ?%

Question: What percentage of the class chose cat?

Step 1: Find the fraction for cat

$1 - \frac{1}{4} - \frac{1}{5}$

= $\frac{20}{20} - \frac{5}{20} - \frac{4}{20}$

= $\frac{11}{20}$

Step 2: Convert to percentage

$\frac{11}{20} \times 100\% = \frac{1100}{20}\% =$ 55%

4. Solving Pie Chart Problems

Example: Stationery sold in a shop

Pens

$\frac{3}{5}$

Rulers

$\frac{1}{10}$

Erasers

(a) What % of stationery sold were pens?

$\frac{3}{5} \times 100\% = \frac{300}{5}\% =$ 60%

(b) What % were erasers?

Erasers = $1 - \frac{3}{5} - \frac{1}{10}$

= $\frac{10}{10} - \frac{6}{10} - \frac{1}{10} = \frac{3}{10}$

$\frac{3}{10} \times 100\% =$ 30%

💡 Tips for Pie Chart Problems:

All fractions/percentages must add up to 1 (or 100%)
To find a missing part: subtract known parts from 1 (or 100%)
Convert fractions to the same denominator when adding/subtracting
Convert to percentage: multiply fraction by 100%

Practice Problems

Practice 1: Reading the pie chart

Look at this pie chart. What percentage of books were Fiction?

ShowHide solution

Fiction = 45 out of 100 books = 45%

As a fraction: $\frac{45}{100} = \frac{9}{20}$

Practice 2: Finding missing percentage

A pie chart shows the favourite fruits of a class: Apples = $\frac{2}{5}$ , Oranges = $\frac{1}{4}$ , Bananas = ?
What percentage of the class chose bananas?

ShowHide solution

Bananas = $1 - \frac{2}{5} - \frac{1}{4}$

= $\frac{20}{20} - \frac{8}{20} - \frac{5}{20}$

= $\frac{7}{20}$

As percentage: $\frac{7}{20} \times 100\% =$ 35%

Practice 3: Finding the quantity

80 students were surveyed about their favourite drink. Use the pie chart to find how many chose Milo.

ShowHide solution

Milo = 35% of 80 students

= $\frac{35}{100} \times 80$

= $\frac{35 \times 80}{100} = \frac{2800}{100}$

= 28 students

Key Takeaways

A pie chart represents the whole: all parts add up to 100%
To find a missing part: subtract known parts from 100%
To convert fraction to %: multiply by 100%
To find a quantity from a percentage: write the percentage over 100 and multiply by the total
Check your answer: all parts should add up to 100%