Question

A mother tells his son, "I was of your present age when you were born". If the mother is now $36,$ how old was his son $5$ years ago?

• A. $13$
• B. $15$
• C. $17$
• D. $20$

Answer 1

The correct option is A $13$

When the son is born, let the age of mother be ${}^{\prime }{x}^{\prime }$ years.
When his son is ${}^{\prime }{x}^{\prime }$ years old, then mother is ${}^{\prime }2x^{\prime }$ years old.
$\Rightarrow 2x=36$ or $x=18$
$\therefore$ $5$ years ago, son is $13$ years old.