The average age of a family of 5 members is 47 years. The average age of the parents is 44 years and the average age of the grandparents is 68 years. What is the age of the child?

1. A

   12 years

2. B

   18 years

3. C

   16 years

4. D

   11 years

Appeared in: DSSSB - 28 August 2019 (Shift-1)

Explanation

• The core of this problem is using the formula: Total Sum = Average × Number of Items.
• First, calculate the total age of the entire family: 5 members × 47 years (average) = 235 years.
• Next, calculate the total age of the parents (2 × 44 = 88 years) and the grandparents (2 × 68 = 136 years).
• The combined age of the parents and grandparents is 88 + 136 = 224 years.
• The child's age is the remaining value after subtracting the known ages from the total family age: 235 - 224 = 11 years.

Why Other Options Were Wrong

• Option A: This is an incorrect calculation. It may result from a minor arithmetic error, such as miscalculating the total age of one of the groups (e.g., 235 - 223 = 12).
• Option B: This value is significantly incorrect and likely stems from a major error in calculation, such as incorrectly summing the ages or misinterpreting the question.
• Option C: This is an incorrect calculation. It could arise from a miscalculation, for example, incorrectly multiplying 5 x 47 as 231 and then subtracting 224, which would give 7, or another combination of errors.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation of average (mean) and finding a missing value as background academic context rather than a clinical decision trigger.
• While this is a mathematics question, the concept of 'average' or 'mean' is fundamental in healthcare.
• Nurses use averages to interpret trends in vital signs (e.g., average heart rate over 24 hours), calculate medication dosages based on average body weight, and understand population health statistics.
• For example, a nurse might calculate the average daily fluid intake for a patient over a week to assess hydration status and report trends to the physician.

How to Approach the Question

• First, identify the main goal of the question, which is to find the age of the child.
• Recognize that the problem is based on the concept of 'average' (mean). Recall the formula: Average = Total Sum / Number of Items.
• Rearrange the formula to find the total sum: Total Sum = Average × Number of Items.
• Apply this formula to calculate the total age for each group mentioned: the entire family, the parents, and the grandparents.
• Subtract the total ages of the parents and grandparents from the total age of the family.
• The result of this subtraction will be the age of the last remaining member, the child.

Concept Tested & Keywords

• Concept Tested: Calculation of average (mean) and finding a missing value.
• Stem keywords: average age, family, 5 members, parents, grandparents, child
• Lead-in keywords: What is the age
• Clinical cues: Age/sex group narrows the expected diagnosis, intervention, or normal reference range.

Question ID

Qw3QcK2yhEo2-130gCbv6i

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