Ex 3.1, 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.” Represent this situation algebraically & graphically.
Let the Current age of Aftab be x years.
& let Current age of Aftab’s daughter be y years.
Given that
“Seven years ago, I was seven times as old as you were then”
Seven years ago,
Age of Aftab = x − 7
Age of Aftab’s daughter = y − 7
Aftab was seven times as old as Aftab’s daughter
(x – 7) = 7(y – 7)
(x – 7) = 7y – 49
x – 7y = 7 − 49
x – 7y = −42
Also,
“three years from now, I shall be three times as old as you will be “
Three years later,
Age of Aftab = x + 3
Age of Aftab’s daughter = y + 3
Aftab will be three times as Aftab’s daughter
(x + 3) = 3(y + 3)
(x + 3) = 3y + 9
x – 3y = 9 − 3
x – 3y = 6
So, our equations are
x – 7y = −42 ...(1)
x – 3y = 6
For Equation (1)
x – 7y = −42
Let x = 0
0 − 7y = −42
−7y = −42
y = (−42)/(−7)
y = 6
So, x = 0, y = 6 is a solution
i.e. (0, 6) is a solution
Let x = 7
7 − 7y = −42
−7y = −42 − 7
y = (−49)/(−7)
y = 7
So, x = 7, y = 7 is a solution
i.e. (7, 7) is a solution
For Equation (2)
x − 3y = 6
Putting x = 0
0 − 3y = 6
−3y = 6
y = 6/(−3)
y = −2
So, x = 0, y = −2 is a solution
i.e. (0, −2) is a solution
Putting y = 0
x − 3(0) = 6
x – 0 = 6
x = 6
So, x = 6, y = 0 is a solution
i.e. (6, 0) is a solution
We will plot both equations on the graph

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

Hi, it looks like you're using AdBlock :(

Displaying ads are our only source of revenue. To help Teachoo create more content, and view the ad-free version of Teachooo... please purchase Teachoo Black subscription.

Please login to view more pages. It's free :)

Teachoo gives you a better experience when you're logged in. Please login :)

Solve all your doubts with Teachoo Black!

Teachoo answers all your questions if you are a Black user!