NCERT Solution Class X Mathematics Pair of Linear Equations in Two Variables Question 1 (Ex 3.1)

Question 1:

Aftab tells his daughter, “Seven years ago, I was seven times as old as you were then. Also, three years from now, I shall be three times as old as you will be.” (Isn’t this interesting?) Represent this situation algebraically and graphically.

Answer:
Let the present age of Aftab be x.

And, present age of his daughter = y

Seven years ago,

Age of Aftab = x − 7

Age of his daughter = y − 7

According to the question,

(x – 7) = 7 (y – 7)

x – 7 = 7y – 49

x – 7y = –42        (1)

Three years hence,

Age of Aftab = x + 3

Age of his daughter = y + 3

According to the question,

(x + 3) = 3 (y + 3)

x + 3 = 3y + 9

x – 3y = 6        (2)

Therefore, the algebraic representation is

x – 7y = –42

x – 3y = 6

For x – 7y = –42

x =  –42 + 7y

The solution table is

For x – 3y = 6,

x = 6 + 3y

The solution table is

The graphical representation is as follows.

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