- NCERT Solutions for Class 9 Maths Chapter 3 Coordinate Geometry Ex 3.1
- NCERT Solutions for Class 9 Maths Chapter 3 Coordinate Geometry Ex 3.2
NCERT Solutions for Class 9 Maths Chapter 3 Coordinate Geometry Ex 3.1
Ex 3.1 Class 9 Maths Question 1.
How will
you describe the position of a table lamp on your study table to another
person?
Solution:
To describe
the position of a table lamp placed on the table, let us consider the table
lamp as P and the table as a plane.
Now, take
two mutually perpendicular edges of the table as the axes OX and OY.
Measure the
perpendicular distance ‘a’ cm of P (lamp) from OY and the perpendicular
distance ‘b’ cm of P (lamp) from OX.
Thus, the
position of the table lamp P is described by the ordered pair (a, b).
Let us assume that the distance of lamp from OY is 18 cm and
the distance of lamp from OX is 16 cm. Then the position of the lamp can be
described as the ordered pair (18, 16).
Ex 3.1 Class 9 Maths Question 2.
(Street
Plan): A city has two main roads which cross each other at the centre of the
city. These two roads are along the North-South direction and East-West
direction. All other streets of the city run parallel to these roads and are
200 m apart. There are 5 streets in each direction. Using 1 cm = 200 m, draw a
model of the city on your notebook. Represent the roads/streets by single
lines.
There are
many cross-streets in your model. A particular cross-street is made by 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:
Let us draw two mutually perpendicular lines as the
two main roads of the city that cross each other at the centre and let us take
it as N-S and E-W direction.
Let us use the scale as 1 cm = 200 m.
Now, draw five streets that are parallel to both the
main roads, to get the given below figure.
(i) From the figure, we can see that only one point has the coordinates as (4, 3). Thus, we can conclude that only one cross street can be referred to as A(4, 3).
(ii) From the figure, we can see that only one point has the coordinates as (3, 4). Thus, we can conclude that only one cross street can be referred to as B(3, 4).