IBPS PO Prelims Model Paper 7 with solutions

Let father’s present age be x years and son’s present age be y years.
∴ x – 5 = 5(y – 5)
⇒ x – 5 = 5y – 25
⇒ x = 5y – 20 ......... (i)
⇒ x + 5 = 3(y + 5)
⇒ x + 5 = 3y + 15
⇒ x = 3y + 10 ......... (ii)
From equations (i) and (ii),
5y – 20 = 3y + 10
⇒ 2y = 30
⇒ y = 15 years
From equation (i),
x = 5 × 15 – 20 = 55 years.
Number of years after which his age will be twice his son’s age = a years
∴ 55 + a = 2 (15 + a)
⇒ 55 + a = 30 + 2a
⇒ a = 55 – 30 = 25 years