BPSC 70th CCE Re-exam Prelims General Studies · Question 144 of 142

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.

• (b)Mother of D — 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)Husband of D — 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)Sister of 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.

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.

The efficient order of work is: generations first, gender second, wording last. Sketch the levels and place everyone before deciding what to call any relationship, because a name applied early gets carried forward and corrupts the rest of the tree. Here the sketch is two levels — A and D on the upper level, B and C on the lower — and it can be drawn in about fifteen seconds. Then check the gender clues, of which there are three: B is a son, C is a brother, D is a father, and A is stated to be female. Only then look at the options, and read each one as a claim about the diagram. Two of the four here can be killed purely on generation, since 'mother of D' and 'sister of D' would move A off the level the diagram puts her on, and the surviving pair differ only in gender, which the stem has already settled. That is the general shape of these items: half the options fail on structure and the other half on a single word, so a candidate who separates the two checks never has to guess.

• 'B is son of A' fixes two things at once — A is one generation above B, and B is male
• 'C is brother of B' places C in B's generation and, on the standard full-sibling convention, makes A a parent of C as well
• 'D is father of C' places D in A's generation and makes D male; the mother and father of the same child are taken to be spouses
• The clue 'A is female' does not affect the structure of the tree at all — it only decides whether the word for A's position is wife or husband
• The sibling link is the load-bearing statement: remove 'C is brother of B' and there is no connection between A and D, and the question becomes unanswerable
• The full tree has two levels: A and D on the parents' level, B and C on the children's level, with A and D joined as a couple and both children hanging from that couple
• Two conventions are always assumed unless a stem says otherwise — siblings share both parents, so no half-brothers or step-parents, and the two parents of a child are spouses; without them almost no puzzle of this type could be decided
• Options (a) and (c) describe the same position in the tree and differ only in the gender of the person occupying it, which is why the stem bothers to state that A is female at all

• Ignoring the gender clue after solving the structure — 'wife of D' and 'husband of D' describe the same position and only the stated sex separates them
• Missing that 'brother' makes A a parent of C too; without that step A and D have no relationship at all
• Introducing possibilities the conventions exclude, such as half-siblings or a step-parent, which would make almost every such puzzle unanswerable

BPSC keeps these short — four clauses, one question, no diagram — so the mark goes to whoever can build the tree in seconds and then read the last clause carefully. The 71st CCE paper shows its other favourite format, a single quoted sentence with a chain of possessives to be unwound. UPSC builds much larger family grids, six or seven people with professions and marital status attached, and often keys them to 'cannot be determined'.

• practice — not a real PYQ

  P is the sister of Q, Q is the son of R, S is the mother of P, and T is the husband of S. How is T related to Q ?

  • (a)Brother
  • (b)Father
  • (c)Uncle
  • (d)Grandfather

  Answer(b) Father — P and Q are siblings and S is their mother, so S's husband T is the father of both; R is simply S under another label as Q's parent.

• practice — not a real PYQ

  In a blood-relation puzzle, the statement 'X is the brother of Y' conveys which two pieces of information ?

  • (a)That X is older than Y, and that X is male
  • (b)That X is male, and that X and Y share the same parents
  • (c)That X is male, and that X is one generation above Y
  • (d)That X and Y are married into the same family

  Answer(b) That X is male, and that X and Y share the same parents — the sibling clue fixes gender and generation together, and on the standard convention it also makes both children of the same two parents.