UPSC Prelims 2025 CSAT, question 55

Topic: Logical reasoning

Q55

$P$ is the brother of $Q$ and $R$ . $S$ is $R$ 's mother. $T$ is $P$ 's father. How many of the following statements are definitely true ?

I. $S$ and $T$ are a couple.

II. $Q$ is $T$ 's son.

III. $T$ is $Q$ 's father.

IV. $S$ is $P$ 's mother.

V. $R$ is $T$ 's daughter.

VI. $P$ is $S$ 's son.

Select the correct answer using the code given below :

Solution.

Answer: (c) Only four

Since $P$ is the brother of $Q$ and $R$ , $P$ is male and $P, Q, R$ are full siblings; since $S$ is $R$ 's mother and $T$ is $P$ 's father, $S$ is the mother and $T$ is the father of all three siblings $P, Q,$ and $R$ , while the genders of $Q$ and $R$ are unknown.
Statements I, III, IV and VI are correct ( $S$ and $T$ are a couple, $T$ is $Q$ 's father, $S$ is $P$ 's mother, and $P$ is $S$ 's son).
Statements II and V are incorrect because the genders of $Q$ and $R$ are not given, so only four statements are definitely true.