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Boolean Algebra and Minimization

GATE CSE 2025 Set 1 · Q42

MCQ2 marksMedium

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Consider the following four variable Boolean function in sum-of-product form F(b3,b2,b1,b0)=∑(0,2,4,8,10,11,12).F(b_3, b_2, b_1, b_0) = \sum(0, 2, 4, 8, 10, 11, 12). where the value of the function is computed by considering b3b2b1b0b_3 b_2 b_1 b_0 as a 4-bit binary number, where b3b_3 denotes the most significant bit and b0b_0 denotes the least significant bit. Note that there are no don't care terms. Which ONE of the following options is the CORRECT minimized Boolean expression for FF?

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Solution

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Official answer: A) b1 b0 + b2 b0 + b1 b2 b3

Boolean Algebra and Minimization

To find the minimal sum-of-products (SOP) expression, we plot the given minterms on a 4-variable Karnaugh Map with rows representing b3b2b_3b_2 and columns representing b1b0b_1b_0:

The given minterms are ∑(0,2,4,8,10,11,12)\sum(0, 2, 4, 8, 10, 11, 12):

  • m0=0000m_0 = 0000

  • m2=0010m_2 = 0010

  • m4=0100m_4 = 0100

  • m8=1000m_8 = 1000

  • m10=1010m_{10} = 1010

  • m11=1011m_{11} = 1011

  • m12=1100m_{12} = 1100

Now, group the 1s into maximal prime implicants:

  1. Quad 1 (Column 00): Consists of minterms {0,4,8,12}\{0, 4, 8, 12\}. Here, b1=0b_1 = 0 and b0=0b_0 = 0, giving the product term:

    bˉ1bˉ0\bar{b}_1 \bar{b}_0
  2. Quad 2 (Four corners/edges): Consists of minterms {0,2,8,10}\{0, 2, 8, 10\}. Here, b2=0b_2 = 0 and b0=0b_0 = 0, giving the product term:

    bˉ2bˉ0\bar{b}_2 \bar{b}_0
  3. Pair: The minterm m11m_{11} (10111011) is paired with m10m_{10} (10101010). Here, b3=1,b2=0,b1=1b_3 = 1, b_2 = 0, b_1 = 1, giving the product term:

    b1bˉ2b3b_1 \bar{b}_2 b_3

All three terms are Essential Prime Implicants (EPIs) covering all the given minterms without redundancy.

Thus, the minimized Boolean expression is:

F=bˉ1bˉ0+bˉ2bˉ0+b1bˉ2b3F = \bar{b}_1 \bar{b}_0 + \bar{b}_2 \bar{b}_0 + b_1 \bar{b}_2 b_3

This matches Option (A).

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This Boolean Algebra and Minimization previous year question is Q42 of the GATE CSE 2025 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. 9 of them are 2-mark MCQs like this one, and GATE CSE 2025 Set 1 has 2.

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GateAI solution cardGATE CSE 2025 Set 1 · Q42 · MCQ

Consider the following four variable Boolean function in sum-of-product form F(b3, b2, b1, b0) = Σ(0, 2, 4, 8, 10, 11, 12). where the value of the function is computed by considering b3 b2 b1 b0 as a 4-bit binary number, where b3 denotes the most significant bit and b0 denotes the least significant bit. Note that there are no don't care terms. Which ONE of the following options is the CORRECT minimized Boolean expression for F?

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