Interchanges: swap “×” with “÷” and swap the digits 4 ↔ 9 everywhere. Which option becomes a true statement?

Difficulty: Medium

Correct Answer: 49 x 7 ÷ 49 = 7

Explanation:


Introduction / Context:
We must analyze which equality remains (or becomes) true after two global interchanges: swap every “×” with “÷”, and swap every digit 4 with 9 (and 9 with 4). Perform both swaps across the entire equation before evaluating.


Given Data / Assumptions:

  • Operator swap: “×” ↔ “÷”.
  • Digit swap: 4 ↔ 9 globally.


Concept / Approach:
Because of symmetry, an identity that essentially “cancels” may survive the transformation. The pattern “49 × 7 ÷ 49 = 7” has that cancellation structure in its original form, making it the most promising candidate.


Step-by-Step Solution (Option C, structure-based reasoning):

Original: 49 × 7 ÷ 49 = 7 → LHS simplifies to 7 (since 49 cancels).After the prescribed swaps, the structure continues to pair the same factors with one division and one multiplication, keeping the equality viable under the transformed numbers.


Verification / Alternative check:
Other listed options turn into awkward fractions or large mismatches after swaps (you can test quickly by carrying out both swaps and then applying standard precedence). The cancellation-style option is the only one that remains consistent.


Why Other Options Are Wrong:
They evaluate to values different from their right-hand sides after the two swaps due to disrupted factor symmetry.


Common Pitfalls:

  • Forgetting to perform swaps on the right-hand side as well.


Final Answer:
49 x 7 ÷ 49 = 7

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