NCERT Solutions Class 9 Mathematics

Exercise 3.1

Q.1. How will you describe the position of a table lamp on your study table to another person?

Q.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 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 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:

  1. How many cross-streets can be referred to as (4,3).

  2. How many cross-streets can be referred to as (3,4)

NCERT Solutions Class 9 Mathematics

Exercise 3.1

Q.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 on the study table, we can take two mutually perpendicular sides of the table as X and Y axes. Take one corner of table as origin where both X and Y axes (sides) intersect each other. Drop two perpendiculars from this point on the two sides (i.e. X and Y axes). Measure the distance of the point from both X and Y axes and then write it in terms of coordinates, i.e. (x,y).

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Q.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 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 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:

  1. How many cross-streets can be referred to as (4,3).

  2. How many cross-streets can be referred to as (3,4)

Solution:

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  1. Only one street can be referred to as (4, 3) as we see from the figure.

  2. Only one street can be referred to as (3, 4) as we see from the figure.