Aftab tells his daughter, "seven years ago, I was seven times as old as you were then. Also, three years from now,

Question

Form the pair of linear equations for the following problems and find their solution by elimination method:

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." Find their present ages.

Answer 1

Let the present age of father i.e. Aftab = x yr

And the present age of his daughter = y yr

Seven years ago,

Aftab’s age = (x – 7)yr

Daughter’s age = (y – 7)yr

According to the question,

(x – 7) = 7(y – 7)

⇒ x – 7 = 7y – 49

⇒ x – 7y = – 42 …(i)

After three years,

Aftab’s age = (x + 3)yr

Daughter’s age = (y + 3)yr

According to the question,

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

⇒ x + 3 = 3y + 9

⇒ x – 3y = 6 …(ii)

Now, we can solve this by an elimination method

On subtracting Eq. (ii) from (i) we get

x – 3y – x + 7y = 6 – ( – 42)

⇒ – 3y + 7y = 6 + 42

⇒ 4y = 48

⇒ y = 12

On putting y = 12 in Eq. (ii) we get

x – 3(12) = 6

⇒ x – 36 = 6

⇒ x = 42

Hence, the age of Aftab is 42 years and age of his daughter is 12 years.