Pointing to a woman, a man said, “She is the daughter of my grandfather’s only son.”
Who is the woman?

Appeared in: AIIMS Delhi NO- 2019

Explanation

The core of the puzzle is the phrase "my grandfather's only son". For the male speaker, this person is unequivocally his Father.
Substituting this relationship into the sentence, it reads: "She is the daughter of my Father.".
The daughter of one's father is one's Sister.

Option B: A cousin is the child of an uncle or aunt. The phrase 'only son' explicitly rules out the possibility of the man having a paternal uncle.
Option C: The woman is the daughter of the man's father, not the man himself.
Option D: An aunt is the father's sister. The woman in the statement is the father's daughter.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Blood Relation Reasoning as background academic context rather than a clinical decision trigger.
While not a clinical question, this type of logical deduction is a foundational skill for critical thinking in nursing.
Nurses must often piece together information from various sources (patient history, lab results, physician's notes) to form a complete picture, a process that mirrors solving logic puzzles.
What if? If the statement had been "...my grandfather's son" (without 'only'), the woman could be either a sister or a cousin, as the grandfather could have had multiple sons. The word 'only' is the key differentiator.

How to Approach the Question

First, identify the speaker (the man) and the person being described (the woman).
Break the relationship statement into parts. Start by decoding the innermost relationship: 'my grandfather's only son'.
Work from the speaker's perspective. 'My grandfather's only son' must be 'my father'.
Substitute this resolved relationship back into the full statement: 'She is the daughter of [my father]'.
Solve the final, simplified relationship: The daughter of your father is your sister.
Finally, match your conclusion with the provided options to find the correct answer.

Concept Tested & Keywords

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Practise the full AIIMS Delhi NO- 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.