Bar Graphs
Graphical representation of data is known as bar graph. Quantity of data are represented in rectangular bars either horizontally or vertically. These bars are of uniform width with equal spacing between them.
The monthly expenditure of a family is given below. Represent the data in the form of a bar graph.
Month 
Jan 
Feb 
March 
April 
May 
Average monthly expenditure (Rs) 
2500 
3000 
1600 
3500 
800 
To draw the bar graph we proceed as follows.
Step 1 : Drawing the axes 
Take a graph sheet. From a point O towards the left hand lower corner, draw two lines OX and OY perpendicular to each other. OX is the horizontal axis and OY is the vertical axis. 

Step 2 : Labelling the axes 
To make a vertical bar graph we will represent the month along the horizontal axis and the expenditure along the vertical axis 

Step 3 : Choosing a scale 
This is an important step in constructing bar graphs. If the scale chosen is too big (e.g. 1 cm = Rs. 2000 in the above example) the bars will become so small that it will be difficult to interpret the data. 

Step 4 : Calculating

The heights of bars should represent the expenditure in the month. This is calculated as follows. 

Step 5 : Drawing the graph 
Draw the five bars, each of width 1 cm, and with 1 cm space between them, with the heights as calculated above. Write the months below the bars and give the graph a title. 