Correct Option (2)
The sum of the ages of the 5 family members three years ago was 80 years.
The average age of the family three years ago was 80/5 = 16 years.
Considering the passage of three years, the sum of the ages of the 5 original family members today would be 80 + (5 × 3) = 80 + 15 = 95 years.
The problem states that the average age of the family today, including the newly added baby (making a total of 6 members), is the same as it was three years ago, i.e., 16 years.
Therefore, the total sum of ages for the 6 family members today is 16 × 6 = 96 years.
The age of the baby is determined by subtracting the current total age of the 5 original members from the current total age of all 6 family members:
Baby's age = 96 – 95 = 1 year.
Incorrect Options:
Options 1 (6 months), 3 (2 years), and 4 (2 years and 6 months) are inconsistent with the calculated age of 1 year for the baby, which is derived directly from the given conditions regarding the family's age progression and the maintenance of the average age.