Class 9 Mathematics
Chapter 3: Coordinate Geometry
Exercise 3.1 – Solutions
Q1. How will you describe the position of a table lamp on your study table to another person?
To describe the position of a table lamp on a study table, we choose two fixed reference lines, such as the two adjacent edges of the table.
Then we tell the distances of the lamp from these two edges.
For example, we may say:
The lamp is 20 cm from the left edge and 30 cm from the front edge of the table.
In this way, the exact position of the lamp can be described.
Q2. Street Plan
A city has two main roads crossing each other at the centre. One road runs in the North-South direction and the other in the East-West direction.
All other streets run parallel to these roads and are 200 m apart. There are 5 streets in each direction.
A crossing of a North-South street and an East-West street is represented by an ordered pair.
For example, if the 2nd North-South street and the 5th East-West street meet, the crossing is written as (2, 5).
Using this convention:
(i) How many cross-streets can be referred to as (4, 3)?
The ordered pair (4, 3) means:
4th street in the North-South direction
3rd street in the East-West direction
These two streets meet at only one point.
Answer: 1 cross-street
(ii) How many cross-streets can be referred to as (3, 4)?
The ordered pair (3, 4) means:
3rd street in the North-South direction
4th street in the East-West direction
These two streets also meet at only one point.
Answer: 1 cross-street
Final Answers
Q1: The position of the table lamp can be described by giving its distances from two fixed edges of the table.
Q2:
(i) 1
(ii) 1