Cartesian product distributes over union: Given A = {a, d}, B = {b, c, e}, and C = {b, c, f}, compute A × (B ∪ C).

Difficulty: Easy

Correct Answer: (A × B) ∪ (A × C)

Explanation:


Introduction / Context:
For sets, the Cartesian product distributes over union: X × (Y ∪ Z) = (X × Y) ∪ (X × Z). This parallels algebraic distributivity.



Given Data / Assumptions:

  • A = {a, d}
  • B = {b, c, e}
  • C = {b, c, f}


Concept / Approach:
Use the identity above to avoid listing all ordered pairs explicitly.



Step-by-Step Solution:
B ∪ C = {b, c, e, f}A × (B ∪ C) = {(a,x), (d,x) : x ∈ {b,c,e,f}}This equals (A × B) ∪ (A × C) by distributivity



Verification / Alternative check:
Explicit enumeration yields 8 ordered pairs, the same as the union of A × B (6 pairs) and A × C (6 pairs) minus their overlap A × {b,c} (4 pairs).



Why Other Options Are Wrong:
Intersection gives too few pairs; empty set is impossible.



Common Pitfalls:
Confusing set-theoretic union/intersection with arithmetic operations.



Final Answer:
(A × B) ∪ (A × C)

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