Revision Notes on A Pie Chart (Circle Graph)

Steps of Construction of Pie Chart

1. Firstly, calculate the total value.
2. Next, calculate the central angle for each component by using formula

3. Draw a circle of convenient radius.
4. Draw a horizontal radius in this circle.
5. Draw radii making central angles corresponding to the value of components, till all the components are exhausted. These radii divide the whole circle into various sectors.
6. Shade each sector with different design. This is the required pie chart.

Question-1

The number of hours spent by a schoolboy on different activities in a working day is given below: Present the information in the form of a pie chart.

 

Activities	Sleep	School	Home	Play	Others	Total
Number of Hours	8	7	4	2	3	24

Solution:

Here, the total number of hours = 24

So,

The central angle = (component value/24) × 360°

The central angle for each activity will be calculated as follows:

 

Activity	Number of Hours	Central Angle
Sleep	8	8/24 × 360° = 120o
School	7	7/24 × 360° = 105o
Home	4	4/24 × 360° = 60o
Play	2	2/24 × 360° = 30o
Others	3	3/24 × 360° = 45o

 

Now, the pie chart can be constructed by using the given data.

Steps to construct:

Step 1: Draw the circle of an appropriate radius.

Step 2: Draw a vertical radius anywhere inside the circle.

Step 3: Choose the largest central angle. Here, it is 120^o. Construct a sector of central angle 120^o whose one radius coincides with the radius drawn in step 2, and the other radius is in a clockwise direction to the vertical radius.

Step 4: Construct other sectors representing other values in a clockwise direction in descending order of magnitudes of their central angles.

Step 5: Shade the sectors so obtained by different colours and label them as shown in the below figure.

2. Employees of a company have been categorised according to their religions as given below:

Religious	Hindu	Muslim	Sikh	Christian	Others	Total
Number of Workers	420	300	225	105	30	1080

Draw a pie chart to represent the above information.

Solution:

Here, the total number of workers = 1080

So,

The central angle = (component value/1080) × 360°

The central angle for each activity will be calculated as follows:

Religious	Number of Workers	Central Angle
Hindu	420	420/1080 × 360° = 144
Muslim	300	300/1080 × 360° = 100
Sikh	225	225/1080 × 360° = 75
Christian	105	105/1080 × 360° = 35
Others	30	30/1080 × 360° = 10

 

Now, the pie chart can be constructed by using the given data.

Steps to construct:

Step 1: Draw the circle of an appropriate radius.

Step 2: Draw a vertical radius anywhere inside the circle.

Step 3: Choose the largest central angle. Construct a sector of a central angle, whose one radius coincides with the radius drawn in step 2, and the other radius is in a clockwise direction to the vertical radius.

Step 4: Construct other sectors representing other values in a clockwise direction in descending order of magnitudes of their central angles.

Step 5: Shade the sectors so obtained by different colours and label them as shown in the below figure.