The present average age of a family of five members is 26 years. If the present age of the youngest member in the family is ten years, then what was the average age of the family at the time of the birth of the youngest member ? (Assume no death occurred in the family since the birth of the youngest).

A. 18 years
B. 14 years
C. 20 years
D. 16 years

Present total age of the members = 26(5) = 130 years.

Present age of the youngest member = 10 years
Present total age of the remaining four members = 130 -10 = 120 years
Their average age at the time of the birth of the youngest member = [120 – (4 * 10)] / 4 = 30 – 10 = 20 years