Question

A man is four times as old as his son. In five years he will be only three times as old as his son. What is the man's present age?

Answer 1

Man's present age : 40 years old.

Explanation:

Let man's age = `a`
Let son's age = `b`

Since a man is 4 times as old as his son, therefore
`a` = `4b`

In 5 years, he will only be 3 times as old as his son, therefore
`a+5 = 3(b+5)`

Apply substitution method :
`4b + 5 = 3b + 15`

`b = 10`

∴ `a = 40`