If C is brother of B, B is son of A, D is father of C and A is female, then A is

Question

UnlockIAS · Accepted Answer

Correct — A, Wife of D. Take the four statements in the order that builds the tree rather than the order they are printed in. 'B is son of A' places A one generation above B and fixes B as male. 'C is brother of B' places C in the same generation as B and fixes C as male; in these puzzles a brother means a full sibling, so C and B share both parents, which means A is a parent of C as well. 'D is father of C' places D one generation above C, in the same generation as A, and fixes D as male. Now the last clue does its work: 'A is female'. A is a parent of C and is female, so A is the mother of C. D is the father of the same child. The mother and the father of one child are, in the convention these puzzles are written on, husband and wife — so A is the wife of D. Two things are worth noticing about the construction. First, the clue 'A is female' is not decoration; without it the relationship between A and D would be fixed but the word for it would not, since a parent of C paired with D could be described as either the wife or the husband. The paper supplies both readings as options (a) and (c) precisely to punish a candidate who solves the structure and then ignores the gender line. Second, the whole chain runs through the sibling link. If C were not B's brother, nothing would connect A to D at all — A would simply be B's mother and D would be an unrelated father — and the question would have no answer. That single word 'brother' is what welds the two halves of the family together, and reading past it is the commonest way to lose the mark.

Why the other options are wrong — (b) Puts A a generation above D, but the chain places them in the same generation — both are parents of C. Test it and it breaks: if A were D's mother then D's son C would be A's grandson, while B is A's own son, so B would be C's uncle rather than his brother, contradicting the first statement.  (c) Gets the relationship right and the gender wrong. A is the spouse of D, but the stem states in as many words that A is female, so the word required is wife. This is the option for a candidate who solves the family tree correctly and then answers before reading the last clause — which is exactly what the clause was inserted to catch.  (d) Makes A the paternal aunt of C rather than a parent. But A must be a parent of C, because C is the brother of B and B is A's son. The same person cannot be both C's mother and C's father's sister, so this option contradicts the sibling link.

Concept: Blood-relation questions are solved by building a diagram, not by reasoning in sentences, because the sentences are written to be hard to hold in the head. The standard notation is small: put each generation on its own horizontal level, join a married pair with a double line, drop a vertical line from a couple to their children, and mark gender with a plus or minus, a circle or a square — anything consistent. Then convert each clue into a mark on the diagram before drawing any conclusion. Certain phrases carry two pieces of information at once and should be recorded as two: 'son of' fixes both a generation gap and a gender, 'brother of' fixes both a shared generation and a gender, 'father of' fixes a generation gap, a gender and, in combination with a known mother, a marriage. Two conventions make these puzzles decidable and are always assumed unless the question says otherwise: siblings share both parents, so no half-brothers or step-parents; and the two parents of a child are spouses. Where an examiner wants to break a convention, the stem says so, and where the data genuinely run out, papers offer an explicit 'cannot be determined' option — UPSC has keyed that option more than once.

State PCS 2025 Q144 — Science & Technology PYQ with Answer

State PCS 2025 Q144 — Science & Technology PYQ with Answer