The average age of a family of 10 members is 25 years. If the age of the youngest member of the family is 15 years, then the average age of the members of the family just before the birth of the youngest member was approximately:

\(\frac{100}{9}\) years 

Average age of a family of 10 members is = 25 years

Sum of the age of 10 members = 25 × 10 = 250 years

If the age of youngest member is = 15 years

Sum of the age of 9 members at the time of birth of youngest member = 250 - 10 × 15

= 200 - 150

= 100 years

Hence Average age of 9 members is  = \(\frac{100}{9}\) years