UPSC Prelims 2016·CSAT·Quantitative Aptitude·Arithmetic

The sum of the ages of 5 members comprising a family, 3 years ago was 80 years. The average age of the family today is the same as it was 3 years ago, because of an addition of a baby during the intervening period. How old is the baby?

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Last updated 23 May 2026, 3:31 pm IST
  1. A6 months
  2. B1 yearCorrect
  3. C2 years
  4. D2 years and 6 months

Explanation

Here is the step by step explanation: 1. Calculate the total age of the 5 members 3 years ago: The sum was 80 years. 2. Calculate the average age 3 years ago: Average equals Total Sum divided by Number of members, which is 80 divided by 5. This equals 16 years. 3. Calculate the total age of the original 5 members today: Each of the 5 members has aged by 3 years. So, 5 multiplied by 3 equals 15 years added to the previous sum. The sum for these 5 members today is 80 plus 15, which equals 95 years. 4. Calculate the total age of the family today including the baby: The problem states the average age today is the same as it was 3 years ago, which is 16 years. There are now 6 members in the family. So, the total sum today is 16 multiplied by 6, which equals 96 years. 5. Find the age of the baby: Subtract the sum of the 5 members from the total sum of the 6 members. 96 minus 95 equals 1 year. The baby is 1 year old. The correct option is B.
Quantitative Aptitude: The sum of the ages of 5 members comprising a family, 3 years ago was 80 years. The average age of the family today is t

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