Pointing to an old man, a boy said, “His only daughter is the mother of my only sister.” How is the boy related to the old man?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Grandson
A brother and a sister have the same mother. The son of a man’s daughter is his grandson.
The mother of the boy’s sister is also the boy’s mother
That mother is the old man’s only daughter
The boy is the son of the old man’s daughter: he is the old man’s grandson
Why the other options are incorrect
Option (2) Son — Incorrect. The boy’s mother is the old man’s daughter, so the old man is the boy’s grandfather, not his father.
Option (3) Brother — Incorrect. The boy is the son of the old man’s daughter, two generations below him.
Option (4) Son-in-law — Incorrect. A son-in-law is the husband of a daughter; the boy is the daughter’s son.