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.
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.
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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).
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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.
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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.
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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.
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Further, a linear graph has data which forms into a straight line and has two variables in the two axes.
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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.
FAQs on Introduction to Graphs
1. What is a graph in Class 8 Maths and what is its main purpose?
In mathematics, a graph is a visual diagram used to represent data or values in an organised manner. Its main purpose is to make complex information easier to understand by showing relationships and trends. For example, a graph can quickly show if a company's sales are increasing or decreasing over a year, which is much clearer than looking at a table of numbers.
2. What are the main types of graphs covered in the CBSE Class 8 syllabus for the 2025-26 session?
According to the NCERT syllabus for Class 8, you will primarily learn about four main types of graphs:
- Bar Graph: Used for comparing quantities of different categories, like the number of students in different sports.
- Pie Chart (or Circle Graph): Shows the proportion of each category as a part of a whole, such as the percentage breakdown of a student's daily activities.
- Histogram: A special type of bar graph that represents data in continuous intervals, like the number of people in different age groups (0-10, 10-20, etc.).
- Line Graph: Displays how data changes continuously over a period, making it ideal for tracking things like temperature changes throughout a day.
3. What is the difference between a bar graph and a histogram?
The key difference lies in the type of data they represent. A bar graph is used for discrete, separate categories (e.g., flavours of ice cream), and there are gaps between the bars. A histogram is used for continuous data organised in intervals (e.g., height ranges), and the bars are adjacent to each other with no gaps, showing the continuous nature of the data.
4. What are the coordinate axes and the origin in a graph?
In a graph, the coordinate axes are two perpendicular lines that create a framework for plotting points. The horizontal line is called the x-axis, and the vertical line is called the y-axis. The point where these two axes intersect is known as the origin, which has the coordinates (0, 0).
5. How do you locate a point on a graph using coordinates like (4, 5)?
A point is located using an ordered pair called coordinates (x, y). The first number is the x-coordinate, and the second is the y-coordinate. To plot the point (4, 5):
- Start at the origin (0,0).
- Move 4 units along the horizontal x-axis (to the right).
- From there, move 5 units up, parallel to the vertical y-axis.
- The spot where you land is the location of the point (4, 5).
6. Can the coordinates (2, 6) and (6, 2) represent the same point on a graph? Explain why.
No, (2, 6) and (6, 2) represent two completely different points. The order of the numbers in coordinates is crucial. For the point (2, 6), you move 2 units on the x-axis and 6 units on the y-axis. For (6, 2), you move 6 units on the x-axis and 2 units on the y-axis. Their different positions on the graph make them unique points.
7. What is the difference between an independent and a dependent variable in a line graph?
In a line graph, the two variables are related but distinct:
- An independent variable is the one that is changed or controlled, and it does not depend on the other variable. It is always plotted on the x-axis (e.g., time).
- A dependent variable is the one being tested and measured, and its value depends on the independent variable. It is plotted on the y-axis (e.g., the temperature at a certain time).
For instance, in a graph of car speed versus time, time is independent, and speed is dependent on time.
8. How can understanding graphs from this chapter be useful in real life?
Understanding graphs is a practical skill used in many everyday situations. For example, it helps you:
- Interpret News: Understand charts showing election results, stock market trends, or COVID-19 cases.
- Track Fitness: Plot your workout progress, like distance run over weeks.
- Manage Finances: Create a pie chart of your monthly expenses to see where your money goes.
- Analyse Information: Quickly compare product features or performance data before making a purchase.
