Meaning of the commutative law in Boolean algebra What does the commutative property of Boolean addition and multiplication imply about the ordering of variables in two-input OR and AND operations?

Difficulty: Easy

Correct Answer: the way we OR or AND two variables is unimportant because the result is the same

Explanation:


Introduction / Context:
The commutative law is a foundational identity in Boolean algebra and arithmetic. In logic design, it allows flexibility in wiring and simplifies reasoning: swapping the order of inputs to an AND or OR gate does not change the output.


Given Data / Assumptions:

  • Binary variables A, B representing logical 0/1.
  • Operations: OR (+) and AND (·).
  • We focus on two-input operations for clarity.


Concept / Approach:
Commutative law states: A + B = B + A and A * B = B * A. Therefore, input order to OR or AND gates is irrelevant. This is distinct from the associative law (regrouping more than two terms) and the distributive law (mixing AND/OR with distribution).


Step-by-Step Solution:

State the identities: A + B = B + A; A * B = B * A.Interpretation: swapping inputs does not alter the result.Practical implication: wiring order into a gate can be chosen for layout convenience.


Verification / Alternative check:
Truth tables confirm equality for all 4 input combinations (00, 01, 10, 11). Outputs match irrespective of input order for both OR and AND operations.


Why Other Options Are Wrong:

  • Grouping “any way we want” (Option A) describes associativity, not commutativity.
  • Term-by-term expansion (Option B) references distributivity.
  • Factoring requirement (Option D) is unrelated to commutativity.


Common Pitfalls:
Confusing commutative with associative laws; believing gate pin numbering affects logic (it does not for symmetric gates like AND/OR). Non-commutative logic operations exist in other algebras, but not for standard Boolean AND/OR.


Final Answer:
the way we OR or AND two variables is unimportant because the result is the same

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