Circle Graph or Pie Chart
Have you ever come across data represented in circular form as shown?
Age groups of people in a town
These are called circle graphs. A circle graph shows the relationship between a whole and its parts.
Here, the whole circle is divided into sectors. The size of each sector is proportional to the activity or information it represents.
Now, add up the fractions for all the activities. Do you get the total as one?
A circle graph is also called a pie chart.
Try these
1. Answer the following questions based on the pie chart given
(i) Which type of programmes are viewed the most?
(ii) Which two types of programmes have number of viewers equal to those watching sports channels?
2. Each of the following pie charts gives you a different piece of information about your class. Find the fraction of the circle representing each of these information
Fraction of the girls in class =
Fraction of the boys in class =
Fraction of students walking to school =
Fraction of students coming to school by bus or car =
Fraction of students coming to school by cycle =
Fraction of students that love Maths =
Fraction of students That hate Maths =
Drawing pie charts
The favourite flavours of ice-creams for students of a school is given in percentages as follows.
| Flavours | Percentage of student preference |
|---|---|
| Chocolate | 50 % |
| Vanilla | 25 % |
| Other flavours | 25 % |
The total angle at the centre of a circle is
The central angle of the sectors will be a fraction of 360°. We make a table to find the central angle of the sectors (below Table).
| Flavours | Students in per cent preferring the flavours | In fractions | Fraction of 360° |
|---|---|---|---|
| Chocolate | 50% | ||
| Vanilla | 25% | ||
| Other flavours | 25% |
Draw a circle with any convenient radius. For the sake of understanding, take r = 1 unit. Mark its centre (O) and a radius (OA).
The angle of the sector for chocolate is 180°. Use the protractor to draw ∠AOB = 180°.
Continue marking the remaining sectors.
For a , the corresponding distance along the circumference is
For a , the distance along the circumference is
For the general case for any radius 'r', the distance along the circumference is
Example 1
Adjoining pie chart gives the expenditure (in percentage) on various items and savings of a family during a month.
2. On a particular day, the sales (in ₹ ) of different items of a baker’s shop are given below.
| Items | Sales ( in ₹) |
|---|---|
| Ordinary bread | 320 |
| Fruit bread | 80 |
| Cakes and Pastries | 160 |
| Biscuits | 120 |
| Others | 40 |
| Total | 720 |
Now, we make the pie chart
Solution:
We find the central angle of each sector. Here the total sale = ₹ 720. We thus have this table.
| Item | Sales (in ₹) | In fractions | Central Angle |
|---|---|---|---|
| Ordinary Bread | 320 | ||
| Biscuits | 120 | ||
| Cakes and pastries | 160 | ||
| Fruit Bread | 80 | ||
| Others | 40 |
Try These
Draw a pie chart of the data given below.
The time spent by a child during a day.
| Activity | Time Spent (hours) |
|---|---|
| Sleep | 8 |
| School | 6 |
| Home work | 4 |
| Play | 4 |
| Others | 2 |
THINK, DISCUSS AND WRITE
Which form of graph would be appropriate to display the following data.
- Production of food grains of a state:
| Year | Production(in lakh tons) |
|---|---|
| 2001 | 60 |
| 2002 | 50 |
| 2003 | 70 |
| 2004 | 55 |
| 2005 | 80 |
| 2006 | 85 |
2. Choice of food for a group of people.
| Favourite food | Number of people |
|---|---|
| North Indian | 30 |
| South Indian | 40 |
| Chinese | 25 |
| Others | 25 |
| Total | 120 |
The daily income of a group of a factory workers.
| Daily Income (in Rupees) | No. of workers(in factory) |
|---|---|
| 75-100 | 45 |
| 100-125 | 35 |
| 125-150 | 55 |
| 150-175 | 30 |
| 175-200 | 50 |
| 200-225 | 125 |
| 225-250 | 140 |
| Total | 480 |