In a family, each daughter has as many brothers as she has sisters, and each son has twice as many sisters as he has brothers. How many daughters are there in the family?

Appeared in: JSSH Staff Nurse - 2019

Explanation

The solution is a family with 4 daughters and 3 sons.
From a daughter's perspective, she has 3 sisters (the other 3 daughters) and 3 brothers. The numbers are equal, satisfying the first condition.
From a son's perspective, he has 4 sisters (all the daughters) and 2 brothers (the other 2 sons).
The number of sisters (4) is exactly twice the number of brothers (2), satisfying the second condition.

Option A: If there are 2 daughters, there must be 1 son (d-1=s). A son would have 0 brothers and 2 sisters. 2 is not twice 0.
Option B: If there are 3 daughters, there must be 2 sons (d-1=s). A son would have 1 brother and 3 sisters. 3 is not twice 1.
Option D: If there are 5 daughters, there must be 4 sons (d-1=s). A son would have 3 brothers and 5 sisters. 5 is not twice 3.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Logical Reasoning as background academic context rather than a clinical decision trigger.
This question tests logical and analytical reasoning, not direct clinical knowledge.
Strong problem-solving skills are essential for nurses in any setting to analyze patient situations, interpret data, and make sound clinical judgments.
These skills help in prioritizing care, troubleshooting equipment, and adapting to unexpected changes in a patient's condition.

How to Approach the Question

First, carefully read and break down the two distinct statements in the puzzle: one from the daughter's viewpoint and one from the son's.
Translate each statement into a simple logical or mathematical relationship. Let 'd' represent the number of daughters and 's' the number of sons.
For the daughter's statement ('as many brothers as she has sisters'), the equation is s = d - 1, because a daughter doesn't count herself as a sister.
For the son's statement ('twice as many sisters as he has brothers'), the equation is d = 2 * (s - 1), because a son doesn't count himself as a brother.
Solve this system of two simple equations to find the values of 'd' and 's'.
Alternatively, test each of the given options. Plug the number of daughters from an option into the first rule to find the number of sons, then check if this combination satisfies the second rule.

Concept Tested & Keywords

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Practise the full JSSH Staff Nurse - 2019

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