3 yr before, the average age of a family of 5 members was 17 yr. Due to birth of a new child, the average age is same today. The present age of child is?

3 yr before, total age of 5 members = 17 x 5 = 85 yr
∴ The present age of all members of family = 85 + 3 x 5 = 100 yr
Let the age of child be N yr.
∴ Present average age of family including the child
= (100 + N)/6
⇒ 17 = (100 + N)/6
∴ N = 102 - 100 = 2 yr