A pie chart is a way of illustrating information by using sectors of a circle to represent parts of the whole.
Example
A newly qualified teacher (NQT) was given the following information about the ethnic origins of the pupils in a class.
| Ethnic origin | No. of pupils |
|---|
| White |
12 |
| Indian |
7 |
| Black African |
2 |
| Pakistani |
3 |
| Bangladeshi |
6 |
| TOTAL |
30 |
The 30 pupils in the class are classified into five different ethnic origins. The whole pie chart represents the class of 30 pupils, and the five sectors represent 12, 7, 2, 3 and 6 pupils, as shown in the table.
The pie chart has a legend (key) indicating what it represents.
Worked examples
The pie chart below summarises the amount of time spent on various areas of the key stage 2 curriculum in a primary school.
Example one
The total time spent each week on the various areas of the curriculum is 26 hours. How much time is spent on history, geography and music?
The pie chart represents 26 hours.
Look at the pie chart and note that the total time spent on history, geography and music is 25%.
25% is 
, so 25% of the total time is 26 ÷ 4 = 6.5 hours. 6.5 hours = 6 hours and 30 minutes. So 6 hours and 30 minutes is spent on history, geography and music each week.
Example two
The total time spent each week on the various areas of the curriculum is 26 hours. How much time is spent each week on English, mathematics, science and ICT together?
The pie chart represents 26 hours.
Look at the pie chart and note that 58% of the total time was spent on English, mathematics, science and ICT.
58% can be converted to a decimal.
58% = 58 ÷ 100 = 0.58
Using a calculator, 0.58 x 26 = 15.08
To find how many minutes the 0.08 represents in the answer, 15.08 hours, you can calculate: 0.08 x 60 minutes = 4.8 minutes
So to the nearest minute, 15 hours and 5 minutes are spent each week on English, mathematics, science and ICT together.
Using pie charts to compare data
Pie charts are often used to show comparisons between two sets of data.
Worked example
The following pie charts show an analysis of the destinations of pupils leaving a sixth form college.
Which of the following statements are true?
- More pupils went into higher education in 1994 than in 2003
- 136 pupils went into employment in 2003
- More pupils decided on a gap year in 2003 than in 1994.
Statement one
In 1994, 50% of pupils went into higher education and in 2003 only 40%, but the number of pupils is different.
50% of 520 = 1/2 x 520 = 260 pupils
40% of 680 = 40/ 100 x 680 = 272 pupils
There were more pupils in 2003, so statement 1 is false.
Statement two
In 2003, 20% of pupils went into employment.
20% of 680 = 20 ÷ 100 x 680 = 136 pupils
Statement two is true.
Statement three
In 1994, 10% of pupils decided on a gap year.
x 520 = 52 pupils
In 2003, 15% of pupils decided on a gap year.
x 680 = 102 pupils
Statement three is true.