Verified Solution • 2025–26 Session moderate

QJEEM21Mac684: JEE Main 2021 Mathematics - Class 11 JEEM21Mac684 Solution: If P and Q are two statements, then which of the following…

If P and Q are two statements, then which of the following compound statement is a tautology?

Multiple Choice Options

  • A ((P ⇒\Rightarrow Q) ∧\wedge ∼\sim Q) ⇒\Rightarrow (P ∧\wedge Q)
  • B ((P ⇒\Rightarrow Q) ∧\wedge ∼\sim Q) ⇒\Rightarrow Q
  • C ((P ⇒\Rightarrow Q) ∧\wedge ∼\sim Q) ⇒\Rightarrow P
  • D ((P ⇒\Rightarrow Q) ∧\wedge ∼\sim Q) ⇒\Rightarrow ∼\sim P

Step-by-Step Verified Solution

LHS of all the options are same i.e.

((P→Q)∧∼Q)((P \to Q) \wedge \sim Q)

≡(∼P∨Q)∧∼Q\equiv ( \sim P \vee Q) \wedge \sim Q

≡(∼P∧∼Q)∨(Q∧∼Q)\equiv ( \sim P \wedge \sim Q) \vee (Q \wedge \sim Q)

≡∼P∧∼Q\equiv \sim P \wedge \sim Q

(A) (∼P∧∼Q)→Q( \sim P \wedge \sim Q) \to Q

≡∼(∼P∧∼Q)∨Q\equiv \sim ( \sim P \wedge \sim Q) \vee Q

≡(P∨Q)∨Q≠\equiv (P \vee Q) \vee Q \ne Tautology

(B) (∼P∧∼Q)→P( \sim P \wedge \sim Q) \to P

≡∼(∼P∧∼Q)∨∼P\equiv \sim ( \sim P \wedge \sim Q) \vee \sim P

≡(P∨Q)∨∼P\equiv (P \vee Q) \vee \sim P

JEE Main 2021 (Online) 18th March Evening Shift Mathematics - Mathematical Reasoning Question 62 English Explanation

(C) (∼P∧∼Q)→P( \sim P \wedge \sim Q) \to P

≡(P∧Q)∧P≠\equiv (P \wedge Q) \wedge P \ne Tautology

(D) (∼P∧∼Q)→(P∨Q)( \sim P \wedge \sim Q) \to (P \vee Q)

≡(P∧Q)∧(P∨Q)≠\equiv (P \wedge Q) \wedge (P \vee Q) \ne Tautology

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