ST3 Statistics : Pie Charts

Prior Topic ~ Line Graphs

What is a pie?

 Usually, a baked-dish in a round-shaped container

                             

What is a PIE CHART?

Pie Chart: a special chart that uses "pie slices" to show relative sizes of data.

Example:

In a basket, there are 1 apples, 2 pears, 2 bananas and 3 oranges.

Fruit	Numbers
Apple	1
Pear	2
Orange	2
Banana	3
Total	10

There are altogether 10 fruits => there are 10 portions in the pie.

                                         

Using different colours for each fruit:

                                           

                           

Understanding the Pie Chart
The information in the table represented in the Pie Chart:

          
The Pie Chart shows that there are 3 bananas, 2 pears, 2 oranges and 1 apple.

RELATING PIE CHART TO FRACTION/PERCENTAGE/ANGLES

Pie Chart and Fraction

Example   :   What fraction of the fruits is bananas?

Method

   Step1: Compute the total value.

              Total number of fruits = 10

   Step2: Apply formula:  Required value

                                        Total value

               Number of Bananas = 3

               Fraction = 3/10

Pie Chart and Percentage

Example: What is the percentage of orange in the basket?

Method

   Step1: Compute the total value.

              Total number of fruits = 10

   Step2: Required Percent =  Required Value       x 100

                                                   Total Value

Pie Chart to Angles

      

Total degree for a pie chart(circle) is 360^o

Find an angle when given the value

Example: What is the angle representation of apple?

Method

   Step1: Compute total value.

   Step2: Apply Formula Compute Angle :

                        = Required Value x 360^o

                           Total Value

              Angle for Apple = 1/10 x 360^o  = 36^o

Example

The pie chart shows how a class of student travel to school.

                                

(a) What fraction of the students go to school by bus?

Method

   Step1: <Read, underline keywords> Compute the total value

               Total number of student = 10+5+5+20 = 40

   Step2: Apply formula:  Required value

                                        Total value

               Fraction of students go to school by bus = 5 / 40 = 1/8

(b) What percentage of student go to school by MRT?

Method

   Step1: <Read, underline keywords> Compute the total value.

               Total number of student = 10+5+5+20 = 40

   Step2: Required Percent =  Required Value  x 100

                                                   Total Value

              Percentage of students go to school by MRT = 10/40  x 100 = 25%

Example

The pie chart shows the favourite TV programs listed by a group of 60 students.                                    

                          

Find a value when given the angle

(a) How many students like SciFi program?

Method

   Step1: Read, underline keywords. Write total degree = 360^o, and total value = 60

   Step2: Apply Formula : Required value = Angle  x Total Value

                                                                         360

                        SciFi = 90^o
       Number of students who like SciFi = 90/360 x 60 = 15 students

(b) 10 students like Horror, what is the angle representation?

Method

   Step1: Write total degree = 360^o, and total value = 60

   Step2: Apply Formula Compute Angle :

                        = Required Value x 360^o

                           Total Value

               Horror = 10

            The angle representation for horror = 10/60 x 360 = 60^{o
                                          ~~~~ END ~~~~ :)}