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 360o ) / 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% ) / 360o
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 = 90o
Football = 100o
Tennis = 20o
Netball = 30o
Hockey = x o
a) Find the value of x.
x = 360o - 90o - 100o - 20o - 30o = 120o [Sum of angles at the center = 360o]
b) If the number of students who play netball is 45, calculate the total number of students in the third form.
30o (the number of students who play netball) represent 45 students.
1o would represent (45/30) students
Hence the total number of students (represented by 360o) will be
= (45/30) X 360o
= 540 students
c) How much percentage of the total number of students in the third form play basketball?
The percentage of students who play basketball
= (90/360) X 100%