Bar Graphs
Have you seen graphs like this on TV or in a newspaper?
Like pictographs, such bar graphs can help us to quickly understand and interpret information, such as the highest value, the comparison of values of different categories, etc.
However, when the amount of data is large, presenting it by a pictograph is not only time consuming but at times difficult too. Let us see how data can be presented instead using a bar graph.
Let’s take the data collected by Lakhanpal earlier, regarding the number of students absent on one day in each class:
| Class | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| No.of Students | 3 | 5 | 4 | 2 | 0 | 1 | 5 | 7 |
He presented the same data using a bar graph:
Teacher Note : If the students have not noticed, please point out the equally spaced horizontal lines. Explain that this means that each pair of consecutive numbers on the left has the same gap.
Let's solve the below questions?
Answer the following questions using the bar graph:
1. In Class 2,
2. In which class were the maximum number of students absent? Class
3. Which class had full attendance that day? Class
When making bar graphs, bars of uniform width can be drawn horizontally or vertically with equal spacing between them; then the length or height of each bar represents the given number. As we saw in pictographs, we can use a scale or key when the
Let us look at an example of vehicular traffic at a busy road crossing in Delhi, which was studied by the traffic police on a particular day. The number of vehicles passing through the crossing each hour from 6 a.m. to 12:00 noon is shown in the bar graph. One unit of length stands for 100 vehicles.
We can see that the maximum traffic at the crossing is shown by the longest bar, i.e., for the time interval 7–8 a.m. The bar graph shows that
The total number of cars passing through the crossing during the two-hour interval 8.00–10.00 a.m. as shown by the bar graph is about 1000 + 800 =
1. How many total cars passed through the crossing between 6 a.m. and noon?
From the graph, we add the number of vehicles from each time interval.
2. Why do you think so little traffic occurred during the hour of 6–7 a.m., as compared to the other hours from 7 a.m.–noon?
The low traffic during the 6-7 am hour could be because it is very
Most people may not have started their daily activities yet, which is why fewer vehicles are on the road.
3. Why do you think the traffic was the heaviest between 7–8 a.m.?
The traffic was likely the heaviest between 7 am and 8 am because this is a common time for people to commute to work or school.
Many people start their day around this time, leading to a
4. Why do you think the traffic was lesser and lesser each hour after 8 a.m. all the way until noon?
The traffic likely
As the morning progresses, fewer people are travelling, leading to less traffic on the roads.
This bar graph shows the population of India in each decade over a period of 50 years. The numbers are expressed in crores. If you were to take 1 unit length to represent one person, drawing the bars will be difficult! Therefore, we choose the scale so that 1 unit represents 10 crores. The bar graph for this choice is shown in the figure. So a bar of length 5 units represents 50 crores and of 8 units represents 80 crores.
• On the basis of this bar graph, what may be a few questions you may ask your friends?
• How much did the population of India increase over 50 years?
Population in 1951:
Population in 2001:
How much did the population increase in each decade?
1951 to 1961: 44 - 36 =
1961 to 1971: 54 - 44 =
1971 to 1981: 68 - 54 =
1981 to 1991: 84 - 68 =
1991 to 2001: 102 - 84 =