[Mathematic Form 3] Pie Chart

A pie chart can be used to represent statistical data. It is easy to remember the pie chart because, just like the most pies, it is in the shape of circle. 

A pie chart is divided into sectors, whose angles at the center of circle are proportional to the frequency of a certain category of the data. The angles can also be represented as percentages in a pie chart.

To interpret the data in a pie chart, you have to:

i) Determine the angles at the center of each sector. The angle of each sector can be calculated by using the following formula:

Angle of sector = (Quantity represented by sector X 360^o ) / Total quantity

ii) Note that the bigger an angle, the larger is the frequency or quantity represented
To convert the angle of a sector into a percentage, use the following formula:

Percentage = ( Angle of sector X 100% ) / 360^o

Eg:

The pie chart on the right represent the number of students who play basketball, football, tennis, hockey and netball in the third form of secondary school.

Basketball = 90^o
Football = 100^o
Tennis = 20^o
Netball = 30^o
Hockey = x ^o

a) Find the value of x. 
Solution:
x = 360^o - 90^o - 100^o - 20^o - 30^o = 120^o [Sum of angles at the center = 360^o]

b) If the number of students who play netball is 45, calculate the total number of students in the third form.
Solution:
30^o (the number of students who play netball) represent 45 students.
1^o would represent (45/30) students

Hence the total number of students (represented by 360^o) will be
= (45/30) X 360^o
= 540 students

c) How much percentage of the total number of students in the third form play basketball? 
Solution:
The percentage of students who play basketball
= (90/360) X 100%
= 25%