Correct Answer - Option 4 : 2 years

**Given:**

Two years ago, the average age of a family of 8 members was 18 years

**Formula used:**

Average = sum of the observation/number of observation

**Calculation:**

2 year ago,

Average age of family = (2 × 8)/8

⇒ Average age of family 2 year age = 2

So, the average age of family = 18 + 2 = 20

According to the question,

After the born of baby, the average age of family is same today

So, number of family member is 9

Let the new born baby age be P years

⇒ 18 = [(20 × 8) + P]/9

⇒ 162 = 160 + P

⇒ P = 2

**∴The age of the baby 2 years.**