How_To_Be_Good_At_Math

294 STATISTICS •^ MAKING PIE CHARTS

Let’s use the data in this frequency

table to draw a pie chart. The sectors

will represent the different flavours.

The table shows that out of 100

ice creams sold, 45 were lemon

flavour. We can use these numbers in

the formula to find the angle of the

lemon sector: 45 ÷ 100 × 360 = 162°

To find the angles, we take the

frequency for each flavour and

put it into the formula on the right.

Now we do the same for the

other sectors. Then we add up

all the angles to check that they come

to 360°: 162 + 90 + 72 + 36 = 360°

Making pie charts

We can make a pie chart from a frequency table of data using

a pair of compasses and a protractor. There’s a formula to help

us to work out the angle of each sector, or “slice”, on the chart.

Calculating the angles

The first step in drawing a pie chart is

to calculate the angles of the slices.

Frequency

(number of each

flavour sold)

Total frequency

(total number of

ice creams sold)

The angles of all the

sectors in a pie chart

add up to 360°.

Lemon ice

creams sold

(frequency)

36°

162°

72°

90°

Angle of

whole chart

in degrees (°)

Angle of

lemon sector

frequency

× 360°

total frequency

Angle =

Ice cream sales

Flavour Number sold

Lemon

Mango

Strawberry

Mint

45

25

20

10

Total 100

Total number

of ice creams

sold (total

frequency)

Lemon =

Mango = Strawberry =

× 360° = 162°

(^25) × 360° = 90° × 360° = 72° Mint = × 360° = 36°
100
20
100
10
100
45
100
294_295_Making_pie_charts.indd 294 29/02/2016 18:07