 # Introduction to Graphs

Significance of Introduction to Graphs

The mathematics chapter of Introduction to Graphs helps you understand and study the graphical representation of data. The various arrangements of data for the purpose of comparison, analysis, or representation are made using these graphs.

You will be able to learn this Introduction to Graphs Class 8 chapter quickly with the help of our notes. Go through them attentively and make sure you familiarise yourself with the nuances of this chapter. This will eventually help in your academics and understanding or representing a large set of data using graphs.

Introduction to Graphs in Maths

To elaborate this concept, here large volume of numerical data is represented in graphical or pictorial format for the ease of understanding. A graph can have multiple applications such as the comparison between categories, observing the change over a period, data in short intervals, etc.

For any of the applications, the Introduction of Graph Theory discusses several kinds of methods or graphical or pictorial representation of data. A few of them are mentioned below.

1. Bar graphs

As discussed in Class 8 Introduction to Graphs, bar graphs use bars of an identical width to represent the proportion of various quantities or categories. It is widely used for comparison.

Below represents a bar graph which shows profits earned by a company in different years.

Bar graphs can also be used to indicate more than one type of data and then compare and analyse them. An introduction to graph theory west chapter also discusses double bar graphs. Refer to the image below to understand double bar graphs. It represents the maximum temperature rise in four different seasons in two different years (1950 and 2000).

1. Histograms

As per NCERT Class 8 Introduction to Graphs, histograms are similar to bar graphs even though they are a continuous representation of data. Here, the data is grouped in regular intervals but continuous forms. For instance, the histogram shown below represents the distribution or frequency of people in a city as per their age.

1. Pie Charts

In Class 8 Maths Introduction to Graphs, a pie graph is described as a circular representation of the entire data. It is used for cases when a few portions of a whole needs to be represented.

For instance, this pie chart indicates what percentage of people like to watch which genre movie. From the pie chart, it is clear that 30% of people like to watch movies from the romantic genre.

1. Linear and Line Graphs

A line graph is the one where data points vary with the change in time. And as per NCERT Class 8 Maths Introduction to Graphs chapter, linear graphs are the one wherein all the points draw into a straight line.

For instance, observing the change in data over a period can be best observed with a line graph, as shown below.

Further, a linear graph has data which forms into a straight line and has two variables in the two axes.

Since you are familiar with CBSE Class 8 Maths Introduction to Graphs concepts, you will be able to solve the exercise questions with ease. For more comprehensive learning, you can download our Vedantu app and start learning. The study notes and Introduction to Graphs Class 8 questions prepared meticulously by our expert tutors will surely help you clear exams with flying colours.

1. What are the Applications of Graphs in Mathematics?

Ans. When you go through the NCERT Maths Class 8 Introduction to Graphs chapter and understand the basic concept, you will be able to understand its applications not only in mathematics but everyday life.  While handling a large number of data, these can be quickly represented and compared with the use of graphs. For instance, a company’s yearly sale can be represented using a graph, and the total sale in different years can be compared at the end. In other scenarios, a country’s population growth over a period can also be recorded and represented using a line graph.

2. How to Represent a Point on the Cartesian Plane?

Ans. To represent a point on the Cartesian plane, a pair of numbers is used of the form (x,y). Here, x denotes the co-ordinate point lying in the x-axis or horizontal axis, and y denotes the co-ordinate point lying in the y-axis or vertical axis. For instance, if the point is said to be at (2,3), it means the point is 2 graphical units away from the x-axis and 3 graphical units away from the y-axis. Thus the point is plotted in the Cartesian plane with respect to its distance from the point of origin.

3. What do you Understand by Co-ordinate Axis?

Ans. A plane is said to be Cartesian if it has two numbers of lines drawn perpendicular to each other, wherein the horizontal line is termed as x-axis, and the vertical line is known as the y-axis. The co-ordinates of a point in plane are drawn in these lines and are known as the co-ordinate axis. The point of intersection of the two axes in the plane is termed as point of origin, or zero. You will be able to draw any point possible in the two-dimensional plane using these co-ordinate axes.

4. What are the Different Kinds of Variable Used in Graph?

Ans. In this chapter of introduction for graph theory, you will learn about the various kinds of variables used in this concept. These variables are divided into two parts – the dependent variable and independent variable. A dependent variable changes its values as there is a change in values of another quantity. Whereas, an independent variable is the one which does not change its value even if there is change in values of another quantity. For instance, the electric unit consumed is an independent variable whereas the electricity bill is a dependent variable as it will change with change in the value of electric units consumed.