Page 200 - Maths Skills - 8

198 Maths

Central Angle for a Component
The central angle for a component of the pie chart is given as follows:
( Value of the component )
Central angle for a component = Sum of the values of all components × 360°

How to Make a Pie Chart or Circle Graph?
In order to make a pie chart or circle graph, we follow these steps:

Step 1: Calculate the central angle for each component which is given by
( Sum of the values of all components × 360° )
Value of each component

Step 2: Draw a circle of convenient radius.

Step 3: Within this circle, draw a horizontal radius.
Step 4: Starting with the horizontal radius, draw radii making central angles corresponding to the values of
the respective components, till all the components are used up. These radii divide the whole circle into
various sectors.

Step 5: Shade each sector with different colours or designs.
Now let us learn to draw pie charts or circle graphs through some examples.

Let’s Attempt

Example 1: The table below shows the expenditure in percentage incurred on the construction of a house in a
city:

Items Bricks Cement Steel Labour Miscellaneous

Expenditure (in percentage) 15% 20% 10% 25% 30%

Represent the above data by a pie chart.

Solution: Total percentage = 100.
Central angle for each component = ( Value of the component × 360° )
100
Calculation of central angles

Items Expenditure (in percentage) Central Angle

Bricks 15% (15/100 × 360)° = 54°

Cement 20% (20/100 × 360)° = 72°

Steel 10% (10/100 × 360)° = 36°

Labour 25% (25/100 × 360)° = 90°

Miscellaneous 30% (30/100 × 360)° = 108°