Boolean Algebra MCQs (401-500)

  1. The absorption law states that:
    a) A + AB = A
    b) A(A + B) = A
    c) Both a and b
    d) A + A’B = A + B
    Answer: c) Both a and b

  2. The involution law in Boolean algebra is:
    a) (A’)’ = A
    b) (A’)’ = A’
    c) A + A’ = 1
    d) A·A’ = 0
    Answer: a) (A’)’ = A

  3. The idempotent law is represented by:
    a) A + A = A
    b) A·A = A
    c) Both a and b
    d) A + A’ = 1
    Answer: c) Both a and b

  4. The annulment law states that:
    a) A·0 = 0
    b) A + 1 = 1
    c) A + 0 = A
    d) A·1 = A
    Answer: a) A·0 = 0

  5. Which law justifies the simplification A+A′B=A+BA + A’B = A + B?
    a) Absorption law
    b) Distributive law
    c) Consensus theorem
    d) De Morgan’s law
    Answer: a) Absorption law

  6. The commutative law is expressed as:
    a) A + B = B + A and A·B = B·A
    b) A + A’ = 1
    c) A + 0 = A
    d) A + 1 = 1
    Answer: a) A + B = B + A and A·B = B·A

  7. The associative law is represented as:
    a) (A + B) + C = A + (B + C)
    b) (A·B)·C = A·(B·C)
    c) Both a and b
    d) A + A’ = 1
    Answer: c) Both a and b

  8. Simplify: A(B+C)A(B + C).
    a) AB + AC
    b) A + BC
    c) A + B + C
    d) AB + C
    Answer: a) AB + AC

  9. Simplify: A+BC=(A+B)(A+C)A + BC = (A + B)(A + C).
    a) True
    b) False
    Answer: a) True

  10. Simplify A′B+AB′A’B + AB’:
    a) A ⊕ B
    b) A XNOR B
    c) A + B
    d) A · B
    Answer: a) A ⊕ B

  11. Simplify A+A′BA + A’B:
    a) A + B
    b) A’ + B
    c) AB
    d) A + AB
    Answer: a) A + B

  12. Simplify A+ABA + AB:
    a) A
    b) AB
    c) A + B
    d) B
    Answer: a) A

  13. Simplify A+A′=?A + A’ = ?
    a) 1
    b) 0
    c) A
    d) A’
    Answer: a) 1

  14. Simplify A⋅A′=?A·A’ = ?
    a) 0
    b) 1
    c) A
    d) A’
    Answer: a) 0

  15. Simplify (A+B′)(A′+B)(A + B’)(A’ + B):
    a) A XNOR B
    b) A ⊕ B
    c) A · B
    d) A + B
    Answer: a) A XNOR B

  16. Simplify (A+B)(A′+C)(B+C)(A + B)(A’ + C)(B + C):
    a) AB + A’C
    b) A’ + BC
    c) A + B
    d) A + C
    Answer: b) A’ + BC

  17. Simplify (A+B)(A′+B′)(A′+C)(A + B)(A’ + B’)(A’ + C):
    a) AB’ + A’C
    b) A + BC
    c) A’ + B’C
    d) A + B + C
    Answer: a) AB’ + A’C

  18. Simplify (A+B′)(B+C′)(A + B’)(B + C’):
    a) A·B + B’·C’
    b) A + C’
    c) A + B + C’
    d) A’ + C
    Answer: b) A + C’

  19. Simplify A′B+A′C+BCA’B + A’C + BC:
    a) A’ + BC
    b) A’ + B + C
    c) A + C
    d) B + C
    Answer: a) A’ + BC

  20. Simplify (A+B)(A+B′)(A′+C′)(A + B)(A + B’)(A’ + C’):
    a) AB’ + A’C’
    b) A’ + BC
    c) A + C’
    d) A’ + B’C
    Answer: a) AB’ + A’C’

  21. How many cells are in a 5-variable K-map?
    a) 16
    b) 32
    c) 64
    d) 128
    Answer: b) 32

  1. In a 4-variable K-map, a group of 8 adjacent 1s represents:
    a) One variable term
    b) Two variable term
    c) Three variable term
    d) No simplification
    Answer: a) One variable term

  2. In K-map simplification, grouping 1s in powers of:
    a) 2
    b) 3
    c) 4
    d) 5
    Answer: a) 2

  3. A K-map grouping of 2 adjacent cells eliminates:
    a) 1 variable
    b) 2 variables
    c) 3 variables
    d) None
    Answer: a) 1 variable

  4. In a 3-variable K-map, the corner cells are:
    a) Adjacent
    b) Not adjacent
    c) Opposite
    d) Don’t-care cells
    Answer: a) Adjacent

  5. Don’t-care terms in a K-map are used to:
    a) Simplify expressions
    b) Increase variables
    c) Add redundancy
    d) Remove maxterms
    Answer: a) Simplify expressions

  6. A group of 4 cells in a K-map eliminates:
    a) 2 variables
    b) 3 variables
    c) 1 variable
    d) 4 variables
    Answer: a) 2 variables

  7. In a K-map, adjacent cells differ in:
    a) One variable
    b) Two variables
    c) Three variables
    d) None
    Answer: a) One variable

  8. The Gray code sequence used in a 4-variable K-map ensures:
    a) Only one bit changes between adjacent cells
    b) Two bits change
    c) Random order
    d) Lexicographical order
    Answer: a) Only one bit changes between adjacent cells

  9. A cell represents a minterm if the output is:
    a) 1
    b) 0
    c) Don’t-care
    d) Undefined
    Answer: a) 1

  1. NAND gate is called universal because:
    a) All other gates can be derived from it
    b) It produces a universal output
    c) It has multiple inputs
    d) It uses De Morgan’s law
    Answer: a) All other gates can be derived from it

  2. NOR gate is also universal because:
    a) Any Boolean function can be implemented using NOR gates
    b) It produces a complement output
    c) It is faster
    d) It consumes less power
    Answer: a) Any Boolean function can be implemented using NOR gates

  3. NOT gate using NAND gate:
    a) Connect both inputs together
    b) Invert inputs
    c) Connect one input to 1
    d) Connect one input to 0
    Answer: a) Connect both inputs together

  4. AND gate using NAND gates requires:
    a) Two NAND gates
    b) Three NAND gates
    c) Four NAND gates
    d) One NAND gate
    Answer: b) Three NAND gates

  5. OR gate using NOR gates requires:
    a) Three NOR gates
    b) Two NOR gates
    c) Four NOR gates
    d) One NOR gate
    Answer: a) Three NOR gates

  6. XOR gate using NAND gates requires:
    a) Four NAND gates
    b) Two NAND gates
    c) Three NAND gates
    d) One NAND gate
    Answer: a) Four NAND gates

  7. The output of a NOR gate is 1 only when:
    a) All inputs are 0
    b) All inputs are 1
    c) Any input is 1
    d) Inputs are unequal
    Answer: a) All inputs are 0

  8. The output of a NAND gate is 0 only when:
    a) All inputs are 1
    b) All inputs are 0
    c) One input is 1
    d) Inputs are opposite
    Answer: a) All inputs are 1

  9. A NAND gate is equivalent to:
    a) (A·B)’
    b) (A + B)’
    c) A·B
    d) A + B
    Answer: a) (A·B)’

  10. A NOR gate is equivalent to:
    a) (A + B)’
    b) (A·B)’
    c) A + B
    d) A·B
    Answer: a) (A + B)’

  1. A decoder converts:
    a) Binary code → one active output
    b) One input → binary code
    c) Decimal → binary
    d) Binary → Gray code
    Answer: a) Binary code → one active output

  2. A multiplexer (MUX) selects:
    a) One of many inputs to one output
    b) One output to many inputs
    c) One input to multiple outputs
    d) None of these
    Answer: a) One of many inputs to one output

  3. A demultiplexer (DEMUX) performs:
    a) One input → many outputs
    b) Many inputs → one output
    c) Parallel addition
    d) Encoding
    Answer: a) One input → many outputs

  4. A 2-to-4 decoder requires:
    a) 2 inputs and 4 outputs
    b) 4 inputs and 2 outputs
    c) 4 inputs and 4 outputs
    d) 2 outputs and 4 inputs
    Answer: a) 2 inputs and 4 outputs

  5. A parity generator uses which gate?
    a) XOR
    b) XNOR
    c) AND
    d) NOR
    Answer: a) XOR

  6. A parity checker uses:
    a) XNOR
    b) XOR
    c) NOR
    d) NAND
    Answer: a) XNOR

  7. In logic circuits, fan-in refers to:
    a) Number of inputs to a gate
    b) Number of outputs from a gate
    c) Power rating of gate
    d) Speed of logic gate
    Answer: a) Number of inputs to a gate

  8. In logic circuits, fan-out refers to:
    a) Number of gates that can be driven by one output
    b) Number of inputs per gate
    c) Voltage output
    d) Current consumption
    Answer: a) Number of gates that can be driven by one output

  9. A hazard in a logic circuit refers to:
    a) Unwanted glitch during switching
    b) Extra logic gate
    c) Power failure
    d) Incorrect truth table
    Answer: a) Unwanted glitch during switching

  10. A race condition in digital logic occurs when:
    a) Two signals change simultaneously
    b) Output remains stable
    c) Input is constant
    d) Power is off
    Answer: a) Two signals change simultaneously

  11. 461. A logic circuit that outputs 1 only when all inputs are 1 is called:
    a) OR gate
    b) NOR gate
    c) AND gate
    d) XOR gate
    Answer: c) AND gate


    462. The truth table of a NOT gate has:
    a) 2 inputs and 2 outputs
    b) 1 input and 1 output
    c) 2 inputs and 1 output
    d) 3 inputs and 1 output
    Answer: b) 1 input and 1 output


    463. The Boolean expression A + AB simplifies to:
    a) A
    b) B
    c) AB
    d) A + B
    Answer: a) A


    464. The expression A + A’B simplifies to:
    a) A + B
    b) B
    c) A
    d) A’B
    Answer: a) A + B


    465. The Demorgan’s Theorem states that:
    a) (A + B)’ = A’B’
    b) (AB)’ = A’ + B’
    c) Both a and b
    d) None of the above
    Answer: c) Both a and b


    466. Which gate is called the “universal gate” because any logic function can be built using it?
    a) AND
    b) OR
    c) NAND
    d) XOR
    Answer: c) NAND


    467. A Karnaugh Map (K-Map) is used to:
    a) Add binary numbers
    b) Minimize Boolean expressions
    c) Multiply Boolean terms
    d) Generate truth tables
    Answer: b) Minimize Boolean expressions


    468. A 4-variable K-Map has how many cells?
    a) 8
    b) 12
    c) 16
    d) 24
    Answer: c) 16


    469. The maxterm of variables A, B, and C for the combination (A=0, B=1, C=1) is:
    a) (A + B’ + C’)
    b) (A’ + B + C)
    c) (A + B + C’)
    d) (A’ + B’ + C)
    Answer: b) (A’ + B + C)


    470. In Boolean algebra, A + A’ = ?
    a) 1
    b) 0
    c) A
    d) A’
    Answer: a) 1


    471. In Boolean algebra, A·A’ = ?
    a) 1
    b) 0
    c) A
    d) A’
    Answer: b) 0


    472. The output of a NOR gate is 1 when:
    a) All inputs are 1
    b) All inputs are 0
    c) One input is 1
    d) One input is 0
    Answer: b) All inputs are 0


    473. Which law of Boolean algebra states that A + AB = A?
    a) Absorption Law
    b) Idempotent Law
    c) Distributive Law
    d) DeMorgan’s Law
    Answer: a) Absorption Law


    474. The number of possible combinations for a 3-variable logic system is:
    a) 4
    b) 6
    c) 8
    d) 16
    Answer: c) 8


    475. The Boolean expression (A + B)(A + B’) simplifies to:
    a) A
    b) B
    c) A + B
    d) AB
    Answer: a) A


    476. In K-Maps, grouping 1s together represents:
    a) SOP simplification
    b) POS simplification
    c) Minterm combination
    d) Don’t-care condition
    Answer: a) SOP simplification


    477. The output of an XOR gate is 1 when:
    a) Inputs are equal
    b) Inputs are different
    c) One input is 0
    d) Both inputs are 1
    Answer: b) Inputs are different


    478. Which of the following is NOT a basic logic gate?
    a) NAND
    b) OR
    c) XOR
    d) NOR
    Answer: c) XOR


    479. The complement of (A + B)’ is:
    a) A + B
    b) A’ + B’
    c) AB
    d) A’B’
    Answer: a) A + B


    480. Simplify A’B + AB + A’B’.
    a) A’ + B
    b) A + B’
    c) A + B
    d) A’ + B’
    Answer: a) A’ + B

  1. The Consensus Theorem states that AB+A′C+BC=AB+A′CAB + A’C + BC = AB + A’C.
    Answer: True

  2. The redundant term in AB+A′C+BCAB + A’C + BC is:
    a) BC
    b) AB
    c) A’C
    d) None
    Answer: a) BC

  3. The Shannon Expansion Theorem helps in:
    a) Function decomposition
    b) Gate minimization
    c) Transistor modeling
    d) Power analysis
    Answer: a) Function decomposition

  4. Functional completeness of NAND/NOR means:
    a) Any Boolean function can be implemented
    b) Only AND/OR can be made
    c) They are irreversible
    d) Only XOR functions can be made
    Answer: a) Any Boolean function can be implemented

  5. A 3-variable K-map simplifies functions with:
    a) 8 minterms
    b) 4 maxterms
    c) 16 minterms
    d) 6 variables
    Answer: a) 8 minterms

  6. The term “minterm” corresponds to:
    a) Product term giving 1
    b) Sum term giving 0
    c) Product term giving 0
    d) None
    Answer: a) Product term giving 1

  7. The term “maxterm” corresponds to:
    a) Sum term giving 0
    b) Product term giving 1
    c) Sum term giving 1
    d) Don’t-care
    Answer: a) Sum term giving 0

  8. The Distributive Law in Boolean algebra states:
    a) A(B + C) = AB + AC
    b) A + BC = (A + B)(A + C)
    c) Both a and b
    d) None
    Answer: c) Both a and b

  9. The inverse of De Morgan’s theorem is:
    a) (AB)’ = A’ + B’
    b) (A + B)’ = A’·B’
    c) Both a and b
    d) A’ + B’ = A + B
    Answer: c) Both a and b

  10. Duality principle says:
    a) Every algebraic expression remains valid if + ↔ · and 0 ↔ 1 are interchanged
    b) Every expression becomes invalid
    c) Complement and dual are same
    d) None
    Answer: a) Every algebraic expression remains valid if + ↔ · and 0 ↔ 1 are interchanged

  11. Complementation in Boolean algebra means:
    a) Changing 1 → 0 and 0 → 1
    b) Swapping variables
    c) Multiplying by 0
    d) Adding 1
    Answer: a) Changing 1 → 0 and 0 → 1

  12. Simplify: (A+B+C)(A+B+C′)(A + B + C)(A + B + C’).
    a) A + B
    b) A + C
    c) B + C
    d) A + B + C
    Answer: a) A + B

  13. Simplify: A⋅(A+B′)A·(A + B’).
    a) A
    b) A + B’
    c) AB’
    d) A’
    Answer: a) A

  14. The Boolean variable can take how many values?
    a) 2
    b) 4
    c) 8
    d) Infinite
    Answer: a) 2

  15. The Boolean expression (A+0)(A + 0) simplifies to:
    a) A
    b) 0
    c) 1
    d) A’
    Answer: a) A

  16. The Boolean expression (A⋅1)(A·1) simplifies to:
    a) A
    b) 1
    c) 0
    d) A’
    Answer: a) A

  17. Simplify (A+A′)B(A + A’)B:
    a) B
    b) A
    c) A’
    d) 1
    Answer: a) B

  18. Simplify A+A′B′A + A’B’:
    a) A + B’
    b) A’ + B’
    c) A + B
    d) A’B’
    Answer: a) A + B’

  19. Simplify A+A′B′A + A’B’:
    a) A + B’
    b) A’ + B
    c) A + B
    d) A’B
    Answer: a) A + B’

  20. The K-map method is based on:
    a) Grouping adjacent 1s to simplify Boolean expressions
    b) Converting decimal to binary
    c) De Morgan’s theorem
    d) Logic circuit synthesis
    Answer: a) Grouping adjacent 1s to simplify Boolean expressions

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