In a family, the average age of a father and a mother is 35 years. The average age of the father, mother and their only son is 27…

Question

In a family, the average age of a father and a mother is 35 years. The average age of the father, mother and their only son is 27 years. What is the age of the son?

1. A. 10 Years
2. B. 10.5 years
3. C. 11 Years (Correct answer)
4. D. 12 years

Correct Answer

Option C — 11 Years

Detailed Solution & Explanation

The correct answer is 11 Years.

Key Points

• Father + mother total = 2 × 35 = 70 years.
• Father + mother + son total = 3 × 27 = 81 years.
• The son's age is the difference: 81 − 70 = 11 years.

Additional Information

• Every average problem reduces to Total = Average × Count, and the trick here is that subtracting one total from another isolates the member who was added.
• The same technique answers the mirror question — if a member leaves, the drop in total gives that person's value.
• Note that no individual age of the father or mother can be recovered from the data; only their sum is determined, which is why the question asks only for the son.