The average age of a family of 4 members 3 years ago is 21 years. A baby is born and now the average age of the family is same as before. Find the age of baby.a)8yrsb)9yrsc)10yrsd)11yrse)None of theseCorrect answer is option 'B'. Can you explain this answer?

Question

Answer

ADDING AGE OF ALL 4 MEMBERS AT THE PRESENT = 4*21=84+(4*3)=96

AFTER THE BABY IS BORN (MEMBERS=5) = 5*21=105

SO AGE OF THE BABY = 105-96 = 9years.

answer: 9 years old

Answer

Given:
- Average age of a family of 4 members 3 years ago = 21 years
- A baby is born and now the average age of the family is same as before

To find:
- Age of the baby

Solution:
Let's assume the present age of the family members as follows:
- Father's present age = F
- Mother's present age = M
- Son's present age = S
- Daughter's present age = D
- Baby's present age = B

According to the problem statement, the average age of the family 3 years ago was 21 years. Therefore, we can write the following equation:

(F + M + S + D) / 4 - 3 = 21

Simplifying the above equation, we get:

F + M + S + D = 96

Now, after the birth of the baby, the new average age of the family is still 21 years. Therefore, we can write another equation:

(F + M + S + D + B) / 5 = 21

Simplifying the above equation, we get:

F + M + S + D + B = 105

Substituting the value of F + M + S + D from the first equation, we get:

96 + B = 105

Solving for B, we get:

B = 9

Therefore, the age of the baby is 9 years.

Answer: Option (b) 9 years.

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