This question was previously asked in

IBPS RRB Office Assistant Prelims: 8 August 2021 Shift 1 - Memory Based Paper

Option 2 : 9 years

**Given:**

The average age of father and mother = 33 years

Average of father, mother, and son = 25 years

**Formula used:**

Sum of all observations = Average × Number of observations

**Calculation:**

The average age of father and mother = (33×2) years

⇒ 66 years

The average age of the father, mother, and son = (25×3) years

⇒ 75 years

Required age of son = (75 - 66) years

⇒ 9 years

**∴ The age of the son is 9 years**