Question

The average age of 5 members is 21 years. If the age of the youngest member is 5 years, find out the average age of the family at the birth of the youngest member.

• A. 24 years
• B. 25 years
• C. 20 years
• D. 28 years
• E. None of these

Answer 1

The correct option is C 20 years

Total age of 5 members $=21\times 5=105years$
Total age of 4 members at the birth of the youngest member, i.e., 5 years ago $=105-(5\times 5)=80years$
Before the birth of the youngest member, the family consisted of only 4 members.
Average age of 4 members 5 years ago $=\frac{80}{4}=20$ years.