Blood Relations MCQs for UPSC Prelims

Correct answer: C - Q is the father of P.

Read the expression left to right using the defined operators. 'P + R' means P is the son of R, so R is a parent of P. 'R - Q' means R is the wife of Q. So R is the wife of Q and R is P's mother (a parent), which makes Q the husband of R and therefore the father of P. Hence (c) Q is the father of P. The official UPSC answer key marks this (c).

Correct answer: C - Only four

P is the brother of Q and R, so P, Q and R are siblings and P is male. S is R's mother, so S is the mother of all three siblings. T is P's father, so T is the father of all three. Now test each statement. I: S and T are the mother and the father of the same children, so they are a couple - definitely true. II: Q is T's child, but Q's gender is not given, so 'Q is T's son' is not definite. III: T is the father of all three siblings, so T is Q's father - definitely true. IV: S is the mother of all three siblings, so S is P's mother - definitely true. V: R's gender is not given, so 'R is T's daughter' is not definite. VI: P is male (a brother) and S is his mother, so P is S's son - definitely true. Statements I, III, IV and VI are definitely true, which makes exactly four. The official UPSC key confirms option (c).

Correct answer: B - It is likely that the man's wife was left at home.

The daughters left for a feast and all the male members (the man and his two sons, plus the father who instead stayed away at work) left the home. The only person not accounted for among those who left is the wife. Nothing definitely states she stayed back, so we cannot assert it with certainty; we can only say it is likely she was left at home. The absolute claims ('Only', 'None', 'More than one') overstate what the statements support, while 'It is likely that the man's wife was left at home' is the cautious, defensible inference.

Correct answer: B - T

T is a man married to one of the group members. P and S are unmarried, so T's spouse is not P or S. Q is the brother of P; T (a man) is married, and a man is not married to a brother, so Q is not T's spouse. The only remaining member is R, so T is married to R. Therefore the spouse of R is T.

Correct answer: B - R is S's wife.

Work out the structure across two generations with 3 males, 3 females, two married couples and two unmarried siblings. P and Q form one married couple (the parents); Q is female (a mother-in-law), so P is male. U is P's daughter and so a child. The children of P and Q are U, S and T; R is the in-law who married a child of P and Q (since Q is R's mother-in-law). T is an unmarried male, so the two unmarried siblings are T and U. R married the remaining child S (a male), so R is female and R is S's wife, matching option (b). The three males are P, S, T and the three females are Q, R, U, consistent with the data. Note: this item is contested; some coaching keys list (d) None of the above, but the logical derivation and the official key give R is S's wife, so option (b) is kept with medium confidence.

Correct answer: A - Judge

Known professions: A is the engineer, C is the lawyer, E is the doctor, F is the draughtsman. That leaves the stenographer and the judge for B and D. C (lawyer) is the daughter-in-law of D, so C is married to D's son, and since the judge is married to the lawyer, C's husband is the judge. F is the son of B, and D is the grandmother of F, so D is B's mother and A's wife. A (engineer) is married to the lady stenographer, so D is the stenographer. The remaining profession, judge, belongs to B, who is therefore married to C (the lawyer). Hence B is the Judge.

Correct answer: A - Her brother

The four players are Lakshmi (L), her brother (B), her daughter (D) and her son (S). From clue (i), B and D are on opposite sides of the net. Clue (ii) says the son is diagonally across from the worst player's sibling, so the son is not himself the worst player's sibling, and the worst player must have a sibling among the players. The sibling pairs are L and B (brother and sister) and D and S (sister and brother). The son S is diagonally across from the worst player's sibling, which means the worst player's sibling is on the opposite side from S. Working through the seating, Lakshmi turns out to be the worst player and her brother B is her sibling. By clue (iii), the best and worst players sit on the same side, so the best player is on Lakshmi's side, which is her brother. Hence the best player is her brother.

Correct answer: C - Q

Q is stated to be the brother of P, so Q is definitely a man. P could be male or female (only that Q is P's brother is fixed). S's gender is not determinable. T is a man too, but T is not among options (a)-(c) except Q, and the question asks which of the listed is definitely a man. Among P, S and Q, only Q is certainly male. Hence the answer is Q.