Question

A man is five times as old as his son. Four years ago, he was nine times as old. Find their present ages.

Answer 1

Let us assume the age of the son now = x
Then
The age of the man now = 5x
Now we have to calculate the age of the son and father 9 years ago
Age of the son 4 years ago = x - 4
Age of the man 4 years ago = 5x - 4
Then
5x - 4 = 9(x - 4)
5x - 4 = 9x - 36
5x - 9x = -36 + 4
- 4x = - 32
MUltiplying both sides of the equation by -1 we get
4x = 32
x = 32/4
  = 8
So the present age of the son is 8 years
Present age of the man = 5x
                                       = 5 * 8
                                       = 40 years
So the present age of the man is 40 years and the present age of the son is 8 years.