Thursday 11 December 2014

What do you mean by Bar Graphs?

Understand the maths of a Bar Graph. Click on the link to Watch the VIDEO explanation: 
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Bar Graphs
Let us learn about bar graphs
A Bar chart is the simplest and most widely used graph in which the numerical data is represented by bars or rectangles of equal width.
We should now list some properties of Bar Graph
The width of each bar can be arbitrary chosen, but width of all the bars should be the same.
The space between the consecutive bars should also be the same.
The height or length of a bar is proportional to the numerical data it represents.
Note: the height or length of a bar represents a quantity, whereas its width represents nothing.
There are 3 types of bar graphs
Simple Bar Graph
Double Bar Graph
Divided Bar Graph
Observe the examples of the simple bar graph
Both graphs represent the same data. Each bar represents a class of a student and its heights represents the number of students in that class. Recall that the width of each bar and the spacing between the consecutive bars are arbitrary chosen but uniformity must be maintained. 
Study the example given of a Double Bar Graph
Each pair of bars denotes number of a students in a class. The completely shaded bars represents the number of the girls in a class while the partially shaded bars represents the number of the boys in the same class. The x axis gives the division of standard 9 while the y axis gives the number of the students.
Can you figure out why we need not represent total separately by a third bar in each class
Studied this example of a Divided Bar Graph
This graph represent the same data as that of the double bar graph. Here the length of each bar gives the total number of students in the class. The completely shaded portion represents the number of the girls in the class while the other portion of the bar represents the number of the boys in that class.
Let us now study a problem the table shows the marks obtained by sumit in the annual examination: 

English 50 
Maths 40
Hindi 60
Sanskrit 70
Science 50
Social Studies 54
Represent this data on a graph
Proceed as follows
Set up the scale on the y axis
Let 1 cm represents 10 marks
Let us set the width of each bar to 1 cm and the space between any two consecutive bars to 1 cm.
Using the chosen scale determine the length of the bar corresponding to the marks of each subject.
Draw the bar as shown in the graph. Label the bars correctly.

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