The average age of 10 members of a family is 34 years. If the youngest member is 7 years old, what was the average age (in years) of the family members excluding the youngest member?

Correct option is D

Given:

Average age of 10 family members = 34 years
Age of the youngest member = 7 years

Formula Used:

Average age = (Sum of ages of all members) / (Number of members)
Sum of ages = Average age × Number of members 

Solution:

The total sum of ages of the 10 members is:
Sum of ages = 34 × 10 = 340 years
The sum of ages of the 9 members (before the youngest was born) would be:
Sum of ages before the youngest was born = 340 - 7 = 333 years
The number of family members excluding the youngest member is 9.
The average age of the family members excluding the youngest member is:
Average age before birth = $$\frac{333 }{9 }= 37$$​years
Thus, the average age of the family members excluding the youngest member is 37 years.