Introduction to Graph Class 8 | NCERT Concepts Guide

Understanding graphs is one of the most important skills you will learn in Class 8 Mathematics but did you know graphs can turn complex numbers into easy-to-understand visuals in seconds? Graphs help us visualize data, compare values, and understand relationships between different quantities in a simple and clear way.

If you’ve ever seen charts showing temperature changes, cricket scores, or even your daily screen time—you’ve already seen graphs in action!

In this blog, we will explain the complete NCERT concept of “Introduction to Graphs (Class 8)” in a simple and easy way, exactly at your level. You will also get practice questions (without solutions) to test your understanding.

Why Learn Graphs in Class 8?

Graphs are not just part of your syllabus and they are used in real life everywhere:

• Weather reports

• Business sales data

• Sports statistics

• Science experiments

Learning graphs helps you:

• Understand data easily

• Improve problem-solving skills

• Prepare for higher math concepts

What is a Graph? (Class 8 Concept)

A graph is a visual representation of data using lines, points, or curves on a plane.

Instead of reading numbers in a table, graphs allow us to:

• See patterns quickly

• Compare values easily

• Understand relationships between two quantities

Cartesian Plane (Coordinate Plane) – Class 8

Before plotting graphs, you must understand the Cartesian Plane.

What is a Cartesian Plane?

It is a flat surface formed by two perpendicular lines:

• Horizontal line (X-axis)

• Vertical line (Y-axis)

These axes intersect at a point called the origin (0,0).

Quadrants in Cartesian Plane

The plane is divided into four parts called quadrants:

1. First Quadrant → (+, +)

2. Second Quadrant → (-, +)

3. Third Quadrant → (-, -)

4. Fourth Quadrant → (+, -)

Coordinates of a Point

A point on a graph is represented as:

(x, y)

• x → horizontal distance

• y → vertical distance

Example:

Point (3, 2) means:

• Move 3 units right

• Move 2 units up

Plotting Points on Graph – Class 8

Steps to Plot a Point:

1. Draw X and Y axes

2. Mark equal units on both axes

3. Start from origin (0,0)

4. Move along x-axis

5. Then move along y-axis

6. Mark the point

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Example Points:

• (2, 3)

• (-4, 2)

• (3, -5)

• (-2, -3)

Types of Graphs in Class 8

According to NCERT, students mainly learn:

1. Line Graph

A line graph shows how data changes over time.

Example:

• Temperature change in a week

• Marks scored in exams

Points are plotted and connected using straight lines.

2. Bar Graph (Revision from previous classes)

A bar graph represents data using rectangular bars.

• Height of bar = value

• Used for comparison

Linear Graphs – Class 8 Core Concept

This is the most important topic in the chapter.

What is a Linear Graph?

A graph that forms a straight line is called a linear graph.

It represents a linear relationship between two variables.

Example:

If:
y = x

Then points will be:

• (1,1)

• (2,2)

• (3,3)

When plotted → straight line

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Variables in Graphs

Graphs usually involve two variables:

• Independent variable (x)

• Dependent variable (y)

Example:

If:
y = 2x

Then:
y depends on x

Table Formation (Very Important for NCERT)

Before drawing a graph, we create a table:

Then plot points.

Graph of a Linear Equation in Two Variables

In Class 8, you will learn how to plot equations like:

• y = x + 2

• y = 2x

• y = x - 1

Steps:

1. Choose values of x

2. Find corresponding y

3. Make table

4. Plot points

5. Join points → straight line

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Reading a Graph

Graphs are not just for drawing and you also need to interpret them.

Example Questions:

• What is the value at a certain point?

• Which value is highest?

• What trend is shown?

Real-Life Example of Graphs

Example: Distance-Time Graph

• X-axis → Time

• Y-axis → Distance

This shows how distance changes with time.

Important Points to Remember

• Always label axes properly

• Use equal scale

• Plot points accurately

• Join points neatly

• Graph should be clean and clear

Common Mistakes Students Make

• Wrong scale

• Incorrect plotting

• Confusing x and y values

• Not labeling axes

• graph questions for class 8

Practice Questions (Class 8 – NCERT Level)

 Important: Only questions are provided (no solutions), so try solving them yourself.

Section 1: Basic Concepts

1. Define a graph.

2. What is a Cartesian plane?

3. What is the origin?

4. Name the four quadrants.

5. What are coordinates of a point?

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Section 2: Identify Quadrants

State the quadrant for each point:

1. (3, 4)

2. (-2, 5)

3. (-4, -3)

4. (5, -2)

Section 3: Plotting Points

Plot the following points on graph paper:

1. (2, 3)

2. (4, 1)

3. (-3, 2)

4. (-2, -4)

5. (3, -5)

Section 4: Table to Graph

Draw graph for:

Section 5: Linear Graphs

Plot the graph for:

1. y = x

2. y = 2x

3. y = x + 1

4. y = x - 2

Section 6: Word Problems

1. The cost of 1 pen is ₹5. Draw a graph showing cost vs number of pens.

2. A student studies 2 hours daily. Show graph of total hours vs days.

3. A car travels 40 km per hour. Plot distance-time graph.

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Section 7: Interpretation Questions

Answer based on graph (draw yourself):

1. Which value is highest?

2. What trend do you observe?

3. Is the graph increasing or decreasing?

Section 8: Challenge Questions

1. Plot points for y = 3x and observe the pattern.

2. Can two different equations have the same graph?

3. What happens if x = 0?

Applications of Graphs in Real Life (Class 8)

Graphs are not just limited to your maths textbook—they are widely used in everyday life. Understanding this makes learning graphs more interesting and practical for Class 8 students.

For example, in weather reports, graphs show how temperature changes over days. In sports, graphs can represent a player’s performance over matches. Similarly, in business, companies use graphs to track sales, profits, and growth.

One of the most common real-life graphs is the distance-time graph. It helps us understand how fast something is moving. If the graph is a straight line, it means the speed is constant. If the line curves or changes, it shows variation in speed.

Graphs also help in:

• Comparing data easily

• Identifying trends (increase or decrease)

• Making predictions based on patterns

By learning graphs in Class 8, you are building a strong foundation for subjects like science, economics, and higher mathematics.

Tips to Score Full Marks in Graph Questions (Class 8)

Graph questions are highly scoring if you follow the correct steps and maintain neatness. Here are some simple tips to help you perform well in exams:

1. Always Use Proper Scale

Choose a scale that fits your graph neatly on the paper. Mention the scale clearly.

2. Label Axes Correctly

• X-axis → horizontal

• Y-axis → vertical
  Always write what each axis represents.

3. Plot Points Carefully

Double-check coordinates before marking. Even a small mistake can affect the entire graph.

4. Use Pencil and Ruler

Graphs should always be neat. Use a sharp pencil and ruler for straight lines.

5. Join Points Properly

For linear graphs, join points with a straight line. Do not leave gaps.

6. Practice Regularly

The more graphs you draw, the easier it becomes. Practice different types of questions from NCERT.

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Final Thoughts

Graphs may seem difficult at first, but once you understand the basics like:

• Cartesian plane

• Coordinates

• Plotting points

…it becomes one of the easiest and most scoring chapters in Class 8 Maths.

A simple trick:
Practice drawing graphs regularly
Focus on accuracy and neatness