Q48. Let P, Q, R, S and T be five statements such that:
I. If P is true, then both Q and S are true.
II. If R and S are true, then T is false.
Which of the following can be concluded? 1. If T is true, then at least one of P and R must be false.
2. If Q is true, then P is true.
Select the correct answer using the code given below:
Detailed Solution
Let's translate the given statements into logical notation: I. P → (Q ∧ S) (If P is true, then Q and S are true) II. (R ∧ S) → ¬T (If R and S are true, then T is false) Now, let's evaluate the conclusions: Conclusion 1: 'If T is true, then at least one of P and R must be false.' This is equivalent to T → (¬P ∨ ¬R).
From statement II, the contrapositive is T → ¬(R ∧ S), which simplifies to T → (¬R ∨ ¬S). So, if T is true, then R is false OR S is false. From statement I, the contrapositive is ¬(Q ∧ S) → ¬P, which simplifies to (¬Q ∨ ¬S) → ¬P.
So, if Q is false OR S is false, then P is false. If T is true, then (¬R ∨ ¬S). If ¬S is true, then from the contrapositive of I, ¬P is true. So, if T is true, then (¬R ∨ ¬P) is true, meaning at least one of P and R must be false.
Thus, Conclusion 1 is correct. Conclusion 2: 'If Q is true, then P is true.' (Q → P) Statement I is P → (Q ∧ S). This means P implies Q, but Q does not necessarily imply P. If Q is true, P could still be false (e.g., Q is true, S is true, but P is false).
Thus, Conclusion 2 is incorrect. Therefore, only Conclusion 1 follows. This question tests a deep understanding of conditional logic and contrapositives, a challenging aspect of CSAT.
More Logical Reasoning & Analytical Ability Questions
Q6. What is X in the sequence 24, X, 12, 18, 36, 90?...
BQ20. Consider the sequence AB_CC_A_BCCC_BBC_C that follows a certain pattern. Which one of the following ...
CQ26. If 7 * 24 = 25 and 12 * 16 = 20, then what is 16 * 63 equal to?...
CQ79. A mobile phone has been stolen. There are 3 suspects P, Q and R. They were questioned knowing that o...
AQ8. If P = +, Q = –, R = ×, S = ÷, then insert the proper notations between the successive numbers in th...
BMore from UPSC 2023 CSAT
Q1. Based on the above passage, the following assumptions have been made: 1. Collection, processing and ...
DQ2. Which one of the following statements best reflects the crux of the passage?...
CQ3. Based on the above passage, the following assumptions have been made: 1. Organic farming is inherent...
BQ4. Which one of the following statements best reflects the most logical, rational and practical message...
CQ5. Based on the above passage, the following assumptions have been made: 1. To implement the Sustainabl...
BAce UPSC with AI-powered Practice
LearnPro's test series adapts to your weak topics and shows real analytics.
Explore Courses →