Suppose that age of the two colleagues be x year and y year
According to question:
⇒ 1/x + 1/y = 5(1/x - 1/y)
⇒ y = 3x/2 - - - - - - - - (i)
Again
⇒ 5xy = 72 (x + y)
⇒ xy/(x + y) = 14.4/1
From equation (i):
⇒ {5x × 3x/2)} = 72 × (x + 3x/2)
⇒ x = 24 year
∴ Age of one of colleagues lies between 24 and 36 year