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NCERT Class 9 Maths Textbook Chapter 3 With Answer Book PDF Free Download
Chapter 3: Coordinate Geometry
3.1 Introduction
You have already studied how to locate a point on a number line. You also know how to describe the position of a point on the line.
There are many other situations, in which to find a point we are required to describe its position with reference to more than one line.
3.2 Cartesian System
You have studied the number line in the chapter on ‘Number System’. On the number line, distances from a fixed point are marked in equal units positively in one direction and negatively in the other.
The point from which the distances are marked is called the origin.
We use the number line to represent the numbers by marking points on a line at equal distances. If one unit distance represents the number ‘1’, then 3 units distance represents the number ‘3’, ‘0’ being at the origin.
The point in the positive direction at a distance r from the origin represents the number r. The point in the negative direction at a distance r from the origin represents the number −r
3.3 Plotting a Point in the Plane if its Coordinates are Given
Until now we have drawn the points for you and asked you to give their coordinates. Now we will show you how we place these points in the plane if we know their coordinates. We call this process “plotting the point”.
| Author | NCERT |
| Language | English |
| No. of Pages | 15 |
| PDF Size | 734 KB |
| Category | Mathematics |
| Source/ Credits | ncert.nic.in |
NCERT Solutions Class 9 Maths Chapter 3 Coordinate Geometry
1. How will you describe the position of a table lamp on your study table to another person?
Solution:
For describing the position of the table lamp on the study table, we take two lines, a perpendicular and a horizontal line. Considering the table as a plane(x and y-axis) and taking perpendicular line as Y-axis and horizontal as X-axis respectively.
Take one corner of the table as the origin where both X and Y axes intersect each other. Now, the length of the table is Y-axis and the breadth is X-axis. From The origin, join the line to the table lamp and mark a point.
The distances of the point from both X and Y axes should be calculated and then should be written in terms of coordinates.
The distance of the point from the X-axis and Y-axis is x and y respectively, so the table lamp will be in (x, y) coordinate.
Here, (x, y) = (15, 25)
2. (Street Plan): A city has two main roads which cross each other at the center of the city. These two roads are along the North-South direction and East-West direction.
All the other streets of the city-run parallel to these roads and are 200 m apart. There are 5 streets in each direction. Using 1cm = 200 m, draw a model of the city in your notebook. Represent the roads/streets by single lines.
There are many cross-streets in your model. A particular cross-street is made of two streets, one running in the North-South direction and another in the East-West direction.
Each cross street is referred to in the following manner: If the 2nd street running in the North-South direction and 5th in the East-West direction meet at some crossing, then we will call this cross-street (2, 5). Using this convention, find:
(i) how many cross–streets can be referred to as (4, 3).
(ii) how many cross–streets can be referred to as (3, 4).
Solution:
- Only one street can be referred to as (4,3) (as clear from the figure).
- Only one street can be referred to as (3,4) (as we see from the figure).
NCERT Class 9 Maths Textbook Chapter 3 With Answer Book PDF Free Download