Line graphs, the mean and pie charts · Usually met around P6
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 add up to 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%. To find 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 it's a third of the day, 24 ÷ 3 = 8 hours. Or write 40 × 30% = 12.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
96 pupils in all: Blue = ? pupils
Show the answer and working
Answer: 96 pupils in all: Blue = 24 pupils
What part of 360° is 90°? 360 ÷ 90 = 4, so 14; 96 ÷ 4 = 24
Example 2
96 pupils in all: Yellow = ? pupils
Show the answer and working
Answer: 96 pupils in all: Yellow = 16 pupils
What part of 360° is 60°? 360 ÷ 60 = 6, so 16; 96 ÷ 6 = 16
Example 3
Food: ?% of the whole
Show the answer and working
Answer: Food: 30% of the whole
The parts make 100%: add the ones you know first, 15 + 40 = 55, 55 + 15 = 70, 100 − 70 = 30, so Food is 30%
Practise it in the game →Line graphs, the mean and pie charts · Free to start, unlimited questions, no download