# NCERT Solutions For Class 9 Math Chapter – 3 Exercise – 3.1

NCERT Solutions For Class 9 Math Chapter – 3 Exercise – 3.1

#### Q1.  How will you describe the position of 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 choose two perpendicular edges of the tables as the axes OX and OY.

Measure the perpendicular distance ‘a’ cm of P (lamp) from OY. Measure the perpendicular distance ‘b’ cm of P (lamp) from OX.

Thus , the position of the table lamp is described by the ordered pair (a,b)

Q2. 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 other streets of the city run  parallel to these roads and are 200 m apart. These 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 – streets 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 Using this  convention find:

• How many cross – streets can be referred to as (4,3).
• How many cross – streets can be referred to as (3,4)

Solution:-

• A unique cross – street as shown by the point A(4,3).
• A  unique cross street as shown by the point B(3,4).

The two cross – streets are uniquely found because of the two reference lines we have used for locating them.