Q. 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:
(a) Only two
(b) Only three
(c) Only four
(d) Only five
Correct Answer : (c) Only four
UPSC Prelims 2025 CSAT
Explanation :
Let’s first restate the given facts in “family‐tree” form:
1. P is the brother of Q and of R.
⇒ P is male, and (in a standard puzzle) P, Q and R share the same two parents.
2. S is R’s mother.
⇒ S is the mother of R (and hence, of P and Q).
3. T is P’s father.
⇒ T is the father of P (and hence, of Q and R).
So the (full) parents of P, Q, R are S (mother) and T (father). Now check each statement:
I. S and T are a couple.
– True (they are mother and father of the same children).
II. Q is T’s son.
– Not necessarily: we know Q is T’s child, but Q’s gender wasn’t given.
III. T is Q’s father.
– True (T is father of P, Q and R).
IV. S is P’s mother.
– True (S is the mother of R, and P is R’s full brother ⇒ same mother).
V. R is T’s daughter.
– Not necessarily: R is T’s child, but R’s gender wasn’t given.
VI. P is S’s son.
– True (P is male and S is the mother of P, Q, R).
Counting the definitely true ones: I, III, IV and VI ⇒ 4 statements.
Answer: (c) Only four.
