# Construction of Bar Graphs

Now we will discuss about the construction of bar graphs or column graph. In brief let us recall about, what is bar graph?

Bar graph is the simplest way to represent a data.

● In consists of rectangular bars of equal width.

● The space between the two consecutive bars must be the same.

● Bars can be marked both vertically and horizontally but normally we use vertical bars.

● The height of bar represents the frequency of the corresponding observation.

For example, let us observe the following data of the bar graph.

The following data gives the information of the number of children involved in different activities.

 Activities Dance Music Art Cricket Football No. of Children 30 40 25 20 53

How to Construct a Bar Graph?

Steps in construction of bar graphs/column graph:

On a graph, draw two lines perpendicular to each other, intersecting at 0.

The horizontal line is x-axis and vertical line is y-axis.

Along the horizontal axis, choose the uniform width of bars and uniform gap between the bars and write the names of the data items whose values are to be marked.

Along the vertical axis, choose a suitable scale in order to determine the heights of the bars for the given values. (Frequency is taken along y-axis).

Calculate the heights of the bars according to the scale chosen and draw the bars.

Bar graph gives the information of the number of children involved in different activities.

Solved examples on construction of bar graphs:

1. The percentage of total income spent under various heads by a family is given below.

 Different Heads Food Clothing Health Education House Rent Miscellaneous % Age of Total Number 40% 10% 10% 15% 20% 5%

Represent the above data in the form of bar graph.

2. 150 students of class VI have popular school subjects as given below:

 Subject French English Maths Geography Science Number of Students 30 20 26 38 34

Draw the column graph/bar graph representing the above data.

Solution:

Take the subjects along x-axis, and the number of students along y-axis

Bar graph gives the information of favourite subjects of 150 students.

3. Number of students in 5 different classes of a school is given below. Read the data and represent it through a bar graph.

Classes

I

II

III

IV

V

Number of Students

150

200

175

250

225

Let us draw a bar graph to represent the given information.

(i) Draw a horizontal axis and mark the points on the line to show class I, class II, class III, class IV, class V at convenient intervals.

(ii) Draw a vertical axis and chose the 1 square = 25 students to mark the points to represent number of students.

(iii) Draw bars of equal thickness for each class keeping equal gap between the bars.

(iv) Give the title as number of students in 5 different classes of a school.

4. The vehicular traffic at a busy road crossing in a particular place was recorded on a particular day from 6am to 2 pm and the data was rounded off to the nearest tens.

 Time in Hours 6 - 7 7 - 8 8 - 9 9 - 10 10 - 11 11 - 12 12 - 1 1 - 2 Number of Vehicles 100 450 1250 1050 750 600 550 200

Bar graph gives the information of number of vehicles passing through the crossing during different intervals of time.

Statistics