Associative law for logical OR — evaluate the statement: “A + (B + C) = (A + B) + C” for Boolean variables A, B, C.

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Boolean algebra mirrors several familiar algebraic laws but with logical operators. The associative law establishes that grouping (parentheses) does not change the outcome for repeated OR or repeated AND operations. This property is fundamental when simplifying logic expressions and designing gate networks.


Given Data / Assumptions:

  • A, B, C are Boolean variables (0 or 1).
  • Operator “+” denotes logical OR.
  • No timing hazards or non-ideal hardware effects are considered—pure logic algebra.


Concept / Approach:
Associativity of OR states that A + (B + C) = (A + B) + C = A + B + C. Because OR is associative, the order of evaluation (grouping) does not alter the truth table. This enables regrouping terms freely to match gate fan-in or to combine like terms during simplification without affecting functionality.


Step-by-Step Solution:

Construct a truth table for A, B, C covering 8 combinations.Compute B + C, then A + (B + C).Compute A + B, then (A + B) + C.Verify equality holds for all rows → expressions are identical.


Verification / Alternative check:
Use set theory analogy: OR corresponds to union; union is associative: A ∪ (B ∪ C) = (A ∪ B) ∪ C. Alternatively, apply Boolean algebra axioms where associativity is a postulate.


Why Other Options Are Wrong:

“Incorrect”: contradicts the associative axiom of OR.“Only true when A = 1” or “mutually exclusive”: associativity is unconditional for Boolean variables.“Arithmetic only”: Boolean OR is also associative by definition.


Common Pitfalls:
Confusing associativity with commutativity or distributivity; all three are valid but serve different rearrangements. Another pitfall is mixing OR with XOR; XOR is also associative but has different algebraic properties.


Final Answer:
Correct

More Questions from Logic Circuit Simplification

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion