### 3 years age, the average age of a family of 5 members was 17 years. A baby having been born, the average age of the family is same today. The present age of the baby is :

A. 1 years B. $1 \frac{1}{2}$ years C. 2 years D. 3 years
According to the question, Average age of a family of 5 members 3 years ago = 17 years sum of ages of a family members = 5 × 17 = 85 years A baby having been born the average age of the family is same today. ∴ Sum of age of a family of 6 members = 17 × 6 = 102 years ∴ Sum of age of a family of 5 members at present $\begin{array}{l}\text{= 85 + 5 × 3}\\ \text{= 85 + 15}\\ \text{= 100 years}\\ \text{∴ Age of child}\\ \text{= 102 – 100 = 2 years}\end{array}$