Egypt Primary 5 Mathematics, Week 29: Drawing a pie chart from data

Pie charts

Week 29 · Pie charts · 3 lessons

Drawing a pie chart from data

Discover Mathematics P5: Term 2, Unit 12, Lessons 1–3

GoalDraw a pie chart from a table of data by finding the angle of each sector.

New words

protractor · a tool for measuring and drawing anglesradius · a line from the centre of a circle to its edgelabel · a word or number written on a chart to say what it shows

Explanation

To draw a pie chart, follow these steps. 1: Find the total of the table. 2: Divide 360° by the total to find the angle for one item. 3: Multiply this angle by each count to get the angle of each sector. 4: Check that the angles add up to 360°. 5: Draw a circle and one radius, then use a protractor to draw each sector one after another. 6: Label each sector and give the chart a title. For example, 24 children chose a favourite colour: red 12, blue 6, green 4 and yellow 2. 360° ÷ 24 = 15° for each child. Red: 12 × 15° = 180°. Blue: 6 × 15° = 90°. Green: 4 × 15° = 60°. Yellow: 2 × 15° = 30°. The angles add up: 180 + 90 + 60 + 30 = 360°.

Colour	Children	Angle
Red	12	12 × 15° = 180°
Blue	6	6 × 15° = 90°
Green	4	4 × 15° = 60°
Yellow	2	2 × 15° = 30°
Total	24	360°

Worked examples

Draw the pie chart for the colours. The red sector is a half circle (180°), then blue is a right angle (90°), green 60° and yellow 30°. Each sector gets its colour name and count.

In the fruit survey of 20 children (mango 8, guava 6, banana 4, orange 2), 360° ÷ 20 = 18° for each child. Mango: 8 × 18 = 144°. Guava: 6 × 18 = 108°. Banana: 4 × 18 = 72°. Orange: 2 × 18 = 36°. The sum is 144 + 108 + 72 + 36 = 360°.

A table gives percents: running 20%, football 40%, swimming 25%, tennis 15%. The percents add up to 100%. Angles: 20% of 360° = 72°, 40% = 144°, 25% = 90°, 15% = 54°. The angles add up to 72 + 144 + 90 + 54 = 360°.

Class activity

Draw your pie chart. Use the class survey of Lesson 1 (or a new one with 20 or 24 answers). Work out the angle for each answer, check that the angles add up to 360°, and draw the chart with a compass and a protractor. Colour the sectors, label them and add a title. Ask a friend two questions about your chart.

Practice

30 children were asked. How many degrees stand for one child? How many degrees for the 5 children who chose cycling?

Drinks survey of 20 children: tea 10, juice 5, milk 5. Find the angle of each sector.

36 people were asked. Each person is 10° on the chart. Counts are 18, 9, 6 and 3. Find the four angles.

The table shows 30%, 45%, 15% and 10%. Find the angle of each sector.

Salma draws sectors of 120°, 100°, 90° and 60°. Can they be a pie chart? Explain.