Four years ago, the average age of a family of four persons was 18 years. During this period, a baby was born. Today if the average age of the family is still 18 years, the age of the baby is

Answer: Option B

Sum of the ages of 4 members, 4 years ago
= (18 × 4) years
= 72 years
Sum of the ages of 4 members now
= (72 + 4 × 4) years
= 88 years
Sum of the ages of 5 members now
= (18 × 5) years
= 90 years
∴ Age of the baby
= (90 - 88) years
= 2 years