Consider the following relationships among members of a family of six persons A, B, C, D, E and F : 1. The number of males equals that of females. 2. A and E are sons of F. 3. D is the mother of two, one boy and one girl. 4. B is the son of A. 5. There is only one married couple in the family at present. Which one of the following inferences can be drawn from the above?
- (a) A, B and C are all females.
- (b) A is the husband of D. ✓ UPSC's answer
- (c) E and F are children of D.
- (d) D is the daughter of F.
Why the answer is (b)
• From statement 1, the family of six has 3 males and 3 females.
• From statement 2, A and E are sons of F, so A and E are male, and F is their parent.
• From statement 4, B is the son of A, so B is male and A is his parent.
• Since A, E, and B are male, the remaining three members (C, D, and F) must be female to satisfy the 3-male/3-female ratio.
• D is the mother of two children (one boy, one girl). Since B is a son of A, B cannot be D's child unless A is D's husband. If A were female, B would be her son, but A is already established as male. Thus, A (male) and D (female) form the only married couple, making A the husband of D.
Why the other options are wrong
- (a) A, B and C are all females.
- A and B are explicitly stated to be sons, making them male, not female.
- (c) E and F are children of D.
- E is a son of F, not a child of D, and F is the parent of A and E, not a child of D.
- (d) D is the daughter of F.
- D is female and the mother of two children, while F is the parent of A and E; D cannot be the daughter of F as F is the grandparent generation relative to B.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2017, held on 18 June 2017. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.