Question

I am three times as old as my son. Five years later, I shall be two and a half times as old as my son. How old I am and how old is my son?

Answer 1

Let, the age of my son is $x$ years.

Then my age is $3x$ years.

Five years hence my son's age will be $x+5$ and that of mine will be $3x+5$.

According to the problem,

$3x+5=2\frac{1}{2}(x+5)$

or, $3x+5=\frac{5}{2}(x+5)$

or, $6x+10=5x+25$

or, $x=15$.

So my son is $15$ years old and my age is $45$ years.