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Question

The average age of a family of 5 members, three years ago, was 17 years. Inspite of the birth of a child in the family during these 3 years the present average age of the family remains the same. What is the present age of the child ?

This question was previously asked in
UGC NET 2022 Paper 1 Question Paper (22-Oct-2022) (Shift 2)
The correct answer is

2 years

 To solve the problem, we need to determine the present age of the child born during the past three years.

  1. Three years ago, the average age of a family consisting of 5 members was 17 years.
  2. The total age of the family members three years ago can be calculated as: 
    \(17 \times 5 = 85 \text{ years}\)
  3. After three years, each of the original 5 members has aged by 3 years, so the total age increase for them is: 
    \(5 \times 3 = 15 \text{ years}\)
  4. Thus, the current total age of the original 5 family members is: 
    \(85 + 15 = 100 \text{ years}\)
  5. In the present, the average age of the family is still given as 17 years. This is now the average for 6 members (the original 5 plus the new child).
  6. The current total age of the family (6 members) is: 
    \(17 \times 6 = 102 \text{ years}\)
  7. The present age of the child will be the difference between the total current age of the family and the total current age of the original 5 members: 
    \(102 - 100 = 2 \text{ years}\)
  8. Thus, the present age of the child is 2 years.

Therefore, the correct answer is 2 years.

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Important Questions from Average

  1. Find the mean marks of the following distribution.
    Marks obtainedNo. of students
    255
    306
    353
    401
  2. The average of first 169 even numbers is
  3. The average weight (in kg) of a family of five members whose weights are 40 kg, 49 kg, 56 kg, 74 kg and 35 kg is:
  4. The average of first 152 odd natural numbers, is:
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