Question : The sum of the present ages of father and son is 90 years. 10 years earlier, the ratio of their ages was 5 : 2 The present age of the father is:
Option 1: $65$ years
Option 2: $68$ years
Option 3: $60$ years
Option 4: $70$ years
Correct Answer: $60$ years
Solution :
Given: The sum of the present ages of father and son is 90 years.
Let the age of the father be $x$ and that of the son be $y$.
So, $x + y = 90$
⇒ $y = 90 - x$ -----------------------------------------(1)
10 years ago,
$ ⇒ \frac{x-10}{y-10} = \frac{5}{2}$
⇒ $2x - 20 = 5y - 50$
⇒$ 2x + 30 = 5y$
By putting the value of $y$ from (1)
⇒ $2x + 30 = 5×(90 – x)$
⇒ $2x + 30 = 450 – 5x$
⇒ $7x = 420$
⇒ $x = 60$
Hence, the correct answer is $60$ years.
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