2 years ago, the average age of a family of 5 members was 16 years. After a baby is born, the average age of family is the same today. Find the present age of the baby.

(1) First find total age of 5 members 2 years ago
(2) Present age of 5 members
(3) Total age of 6 members
(4) Age of baby = Total age of 6 members - Present age of 5 members

We know that,
Average = Sum of Quantities/Number of Quantities

1) First calculate total age of 5 members 2 years ago = (Average age of 5 members x number of members)
First calculate total age of 5 members 2 years ago = (16 x 5) = 80 years

2) Calculate the present age of 5 members
2 years ago, their total age was 80 years. Present age can be calculated as follows:
Present age of 5 members = [80 + (2 x 5)] = 90 years

3) Calculate total age of 6 members considering baby = (16 x 6 ) = 96 years

4) Age of baby = (96 – 90)
= 6 years.