GateAI
Propositional and First-Order Logic

GATE CSE 2016 Set 2 · Q1

NAT1 markEasy

Time

Consider the following expressions: (i) falsefalse (ii) QQ (iii) truetrue (iv) P∨QP \vee Q (v) egQ∨P eg Q \vee P The number of expressions given above that are logically implied by P∧(P⇒Q)P \wedge (P \Rightarrow Q) is ________.

Your answerNumerical answer

Enter a value to check

Solution

Step-by-step verified solution

Official answer: 4

Propositional and First-Order Logic

An expression EE is logically implied by an antecedent AA if and only if A  ⟹  EA \implies E is a tautology (i.e., whenever AA is true, EE must also be true).

First, simplify the premise:

P∧(P⇒Q)≡P∧(egP∨Q)≡(P∧egP)∨(P∧Q)≡false∨(P∧Q)≡P∧QP \wedge (P \Rightarrow Q) \equiv P \wedge ( eg P \vee Q) \equiv (P \wedge eg P) \vee (P \wedge Q) \equiv false \vee (P \wedge Q) \equiv P \wedge Q

Thus, the premise is true only when both PP and QQ are true.

Now test each expression when P=trueP = true and Q=trueQ = true:

  1. (i) falsefalse: Evaluates to falsefalse. Not implied.

  2. (ii) QQ: Evaluates to truetrue. (P∧Q)  ⟹  Q(P \wedge Q) \implies Q is valid.

  3. (iii) truetrue: Evaluates to truetrue. Any formula logically implies truetrue.

  4. (iv) P∨QP \vee Q: Evaluates to true∨true=truetrue \vee true = true. (P∧Q)  ⟹  (P∨Q)(P \wedge Q) \implies (P \vee Q) is valid.

  5. **(v) $

eg Q \vee P∗∗:Evaluatesto**: Evaluates to 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.

Think the official key or this write-up is wrong?

Report error or challenge

Examiner trap

The misconception this question tests

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

Where do you stand for GATE?

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.

One GATE CSE PYQ every morning

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 in GATE CSE

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 Logic

More from GATE CSE 2016 Set 2

Share this solution

A plain-text card for WhatsApp or Telegram study groups.

GateAI solution cardGATE CSE 2016 Set 2 · Q1 · NAT

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

Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.