Question

Robert’s father is $4$ times as old as Robert. If after 5 years, father will be three times as old as Robert, then the present age of Robert’s father is:

• A. $40$
• B. $10$
• C. $60$
• D. $45$

Answer 1

The correct option is A $40$

Let Robert’s age be ${}^{\prime }x$' years.
Then, Robert’s father’s age $=4x$
After 5 years, Robert’s age $=x+5$
and father’s age $=4x+5$
According to the given condition,
$4x+5=3(x+5)$
$\Rightarrow 4x+5=3x+15$
$\Rightarrow 4x-3x=15-5$
$\Rightarrow x=10$
$\Rightarrow 4x=4\times 10=40$
Robert’s present age is 10 years and his father’s age is 40 years.