Consider the following expressions: (i) false (ii) Q (iii) true (iv) P Q (v) eg Q P The number of expressions given above that are logically implied by P (P ⇒ Q) is …
Topic-wise GATE CS PYQs with verified steps
GATE CSE 2016 Set 2 · Q1
Time
Your answerNumerical answer
Solution
Official answer: 4
Propositional and First-Order LogicAn expression is logically implied by an antecedent if and only if is a tautology (i.e., whenever is true, must also be true).
First, simplify the premise:
Thus, the premise is true only when both and are true.
Now test each expression when and :
(i) : Evaluates to . Not implied.
(ii) : Evaluates to . is valid.
(iii) : Evaluates to . Any formula logically implies .
(iv) : Evaluates to . is valid.
**(v) $
eg Q \vee P eg(true) \vee true = false \vee true = true(P \wedge Q) \implies ( eg Q \vee P)$ is valid.
Therefore, the 4 expressions (ii), (iii), (iv), and (v) are logically implied.
Try the question first, then check your work.
Examiner trap
Simplify to , then evaluate which expressions must be true whenever both and are true.
This Propositional and First-Order Logic previous year question is Q1 of the GATE CSE 2016 Set 2 paper. Find more GATE CSE PYQs on Propositional and First-Order Logic in Engineering Mathematics, or browse all GATE CSE PYQs.
Free diagnostic
Take the 20-minute diagnostic: the 3 topics that cost you the most marks, and a rank range. Or sit 5 related Propositional and First-Order Logic PYQs now with no account.
An official question by email at 7 AM IST, with a link to its verified solution. Unsubscribe in one click.
Propositional and First-Order Logic has 18 GATE CSE PYQs across 16 papers from 2011 to 2026. 2 of them are 1-mark NAT questions like this one, and it is the only one in GATE CSE 2016 Set 2.
How GATE tests Propositional and First-Order LogicIndependent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.