Line graphs, the mean and pie charts · Usually met around P6
Drawing pie charts and surveys
One share's angle = 360° ÷ the total.
How to do it
Method
One share's angle = 360° ÷ the total
6 of 30: 6 × 12° = 72°
Another way
Fraction first
630 × 360 = 72
In full
Drawing a pie chart: the whole circle is 360° and stands for everyone. Find what one share is worth first: 30 people in all, so each is 360° ÷ 30 = 12°, and the 6 who chose A are 6 × 12° = 72°. Or find the fraction first: 630 = 15, and 15 × 360° = 72°. Check: the sectors always add up to 360°. To match a pie chart to a table, the biggest amount has the biggest sector; then check each part in turn. A good survey question is fair and clear: it mustn't push people towards an answer (“Football is the most fun, don't you agree?”); its answer choices must cover everything without overlapping (0–2 hours and 2–4 hours overlap at 2) or leaving gaps (add “other”); and it should ask enough people, of different kinds, not just one group.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
A survey asks 120 people, and 49 of them choose “swimming”. On a pie chart, how many degrees is the swimming sector?
Show the answer and working
Answer: 147°
All 120 people are 360°, so each is 360 ÷ 120 = 3°; 49 people are 49 × 3 = 147°.
Example 2
The results of a survey of 24 people are drawn as a pie chart, and the running sector is 270°. How many people chose running?
Show the answer and working
Answer: 18 people
Each person is 360 ÷ 24 = 15°; 270 ÷ 15 = 18 people.
Example 3
Chi-keung wants to ask friends “How many hours of TV do you watch a week?” (whole hours only). Which set of answer choices is best?
- A. 0–1 / 1–6 / 6 or more
- B. 0–1 / 2–6 / 7 or more
- C. 0–1 / 3–6 / 7 or more
- D. 0–1 / 2–6
Choose the right answer
Show the answer and working
Answer: B. 0–1 / 2–6 / 7 or more
Every possible number of hours must fit exactly one choice: no overlaps, no gaps, and “or more” at the end.
Practise it in the game →Line graphs, the mean and pie charts · Free to start, unlimited questions, no download