Question

Roberts father is 4 times as old as Robert. After 5 years, father will be three times as old as Robert. Find their present ages.

Answer 1

Robert= x

Robert's Father= 4x

After 5 years,

Robert= x+5

Robert's Father= 3(x + 5)

4x+5= 3(x+5)

4x+5= 3x+15

4x-3x=15-5

x=5

Therfore,

Robert= 5

Robert's Father= 5x4= 20

Answer 2

Let Robert's age is 'x'
Robert's Father's age is four times as old as Robert = 4x

In five years time, Robert's age is = x + 5
and Robert's Father's age is = 4x + 5

In five years time:
Robert's Father's age = 3 × Robert's age
4x + 5 = 3 (x+5)
4x + 5 = 3x + 15
4x - 3x = 15 - 5
x = 5

Robert's present age = 5
Robert's Father's age = 4 × 5 = 20