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3 years ago, the average age of a family of 5 members was 17 years. A baby having been born, the average age of the family is the same today. The present age of the baby is :
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- 3 years
- 2 years
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1 1 years 2 - 1 year
Correct Option: B
Given that , 3 years ago, the average age of a family of 5 members = 17 years
Total age of 5 members, 3 years ago = 17 × 5 = 85 years
Total present age of 5 members = (85 + 3 × 5) = 100 years
Born on a new baby , the average age of the family of 6 members = 17 years
Total present age of 6 members = 17 × 6 = 102 years
∴ Age of the baby = 102 – 100 = 2 years
Second method to solve this question with the help of given formula :
∴ Here, t = 3, N = 5 , T = 17, n = 1
Present age of baby = nT – Nt
Present age of baby = 1 × 17 – 5 × 3 = 17 – 15 = 2 years
