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Boolean Algebra and Minimization

GATE CSE 2026 Set 1 · Q21

MSQ1 markEasy

Time

Consider the following Boolean expression of a function FF : F(P,Q)=(Pˉ+Q)⊕(PˉQ)F(P, Q) = (\bar{P} + Q) \oplus (\bar{P}Q) Which of the following expressions is/are equivalent to FF ?

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Solution

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Official answer: A) P ⊕ Q; C) P ⊕ Q

Boolean Algebra and Minimization

Given the function:

F(P,Q)=(Pˉ+Q)⊕(PˉQ)F(P, Q) = (\bar{P} + Q) \oplus (\bar{P}Q)

Let A=Pˉ+QA = \bar{P} + Q and B=PˉQB = \bar{P}Q. Recall the definition of XOR: A⊕B=ABˉ+AˉBA \oplus B = A\bar{B} + \bar{A}B.

  1. Calculate ABˉA\bar{B}:

    Bˉ=PˉQ‾=P+Qˉ\bar{B} = \overline{\bar{P}Q} = P + \bar{Q}
    ABˉ=(Pˉ+Q)(P+Qˉ)=PˉP+PˉQˉ+QP+QQˉ=0+PˉQˉ+PQ+0=PˉQˉ+PQA\bar{B} = (\bar{P} + Q)(P + \bar{Q}) = \bar{P}P + \bar{P}\bar{Q} + QP + Q\bar{Q} = 0 + \bar{P}\bar{Q} + PQ + 0 = \bar{P}\bar{Q} + PQ
  2. Calculate AˉB\bar{A}B:

    Aˉ=Pˉ+Q‾=PQˉ\bar{A} = \overline{\bar{P} + Q} = P\bar{Q}
    AˉB=(PQˉ)(PˉQ)=PPˉQˉQ=0\bar{A}B = (P\bar{Q})(\bar{P}Q) = P\bar{P}\bar{Q}Q = 0
  3. Combine terms:

    F(P,Q)=(PˉQˉ+PQ)+0=PˉQˉ+PQF(P, Q) = (\bar{P}\bar{Q} + PQ) + 0 = \bar{P}\bar{Q} + PQ

    This is the standard XNOR function, which can be written as:

    • F(P,Q)=P⊕Q‾F(P, Q) = \overline{P \oplus Q} (Option A)

    • F(P,Q)=Pˉ⊕QF(P, Q) = \bar{P} \oplus Q (Option C)

Options B and D represent XOR (P⊕QP \oplus Q and Pˉ⊕Qˉ=P⊕Q\bar{P} \oplus \bar{Q} = P \oplus Q), which are the negation of FF.

Hence, the correct options are A and C.

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This Boolean Algebra and Minimization previous year question is Q21 of the GATE CSE 2026 Set 1 paper. Find more GATE CSE PYQs on Boolean Algebra and Minimization in Digital Logic, or browse all GATE CSE PYQs.

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Boolean Algebra and Minimization in GATE CSE

Boolean Algebra and Minimization has 36 GATE CSE PYQs across 23 papers from 2011 to 2026. 5 of them are 1-mark MSQs like this one, and GATE CSE 2026 Set 1 has 2.

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GateAI solution cardGATE CSE 2026 Set 1 · Q21 · MSQ

Consider the following Boolean expression of a function F : F(P, Q) = ( P + Q) ⊕ ( PQ) Which of the following expressions is/are equivalent to F ?

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