Stage 12 · Data handling
Pie charts
The whole is 100% or 360°.
How to do it
Method
The whole is 100% or 360°
30% of 40: 40 ÷ 10 = 4, 4 × 3 = 12
Another way
Whole × percentage
40 × 30% = 12
In full
The whole circle is everything: 100%, and the angles at the centre make 360°. The percentages add up to 100%: Red 30%, Blue 25%, Green 20% — add the ones you know first, 30 + 25 = 55, 55 + 20 = 75, 100 − 75 = 25, so Yellow is 25%. How many: find 10% (or 5%) first, then multiply: a class of 40, Blue 30%, 40 ÷ 10 = 4, 4 × 3 = 12 pupils. With angles at the centre: a day of 24 hours, Sleep 120°, 360 ÷ 120 = 3, so a third of the day, 24 ÷ 3 = 8 hours. Or write 40 × 30% = 12 — the same answer.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
24 hours in all: Others = ? hours
Show the answer and working
Answer: 24 hours in all: Others = 3 hours
What part of 360° is 45°? 360 ÷ 45 = 8, so 18; 24 ÷ 8 = 3
Example 2
96 pupils in all: Yellow = ? pupils
Show the answer and working
Answer: 96 pupils in all: Yellow = 48 pupils
What part of 360° is 180°? 360 ÷ 180 = 2, so 12; 96 ÷ 2 = 48
Example 3
Yellow: ?% of the whole
Show the answer and working
Answer: Yellow: 35% of the whole
The parts make 100%: add the ones you know first, 35 + 15 = 50, 50 + 15 = 65, 100 − 65 = 35, so Yellow is 35%
Example 4
Yellow: ?% of the whole
Show the answer and working
Answer: Yellow: 30% of the whole
The parts make 100%: add the ones you know first, 35 + 15 = 50, 50 + 20 = 70, 100 − 70 = 30, so Yellow is 30%
Practise pie charts in the game →Stage 12 · Data handling · Free to start, unlimited questions, no download