Question 69

Logical Reasoning Blood Relations Medium

Introducing a man to her husband a women said, "His brother's father is the only son of my grandfather." How is the women related to this man?

(A) Mother
(B) Aunt
(C) Sister
(D) Daughter
View Dynamic Solution & Explanation
Correct Solution: Option C

Step-by-step Solution:

Family Relation Graph

Family Relation Graph — visualization

Graph for: "His brother's father is the only son of my grandfather." The diagram below shows how the persons relate; it highlights that the woman and the man share the same father (so they are siblings).

Grandfather (only son = Father) Father Woman (speaker) Husband (woman's spouse) Man (introduced) Man's Brother (brother) parent children Same father ⇒ siblings Legend: • Solid grey arrow = parent → child • Dashed red line = spouse • Green box = shows equality used in reasoning
Interpretation used in diagram:
  • "His brother's father" = the father of the man's brother → this is the man's father (shared father).
  • "The only son of my grandfather" = the woman's father.
  • Equating the two gives: man's father = woman's father ⇒ they are siblings ⇒ woman is the man's sister.