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Two years ago, the average age of a family of 8 members was 18 years. After the born of a baby, the average age of the family is same today. What is the age of the baby?
1. 1 year
2. 4 years
3. 3 years
4. 2 years

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Best answer
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.

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