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Difficulty: 2/102024 NMTC 2024 (QII-55)

Cindy was asked by her teacher to subtract 3 from certain number and then divide the result by 9. Instead, she subtracted 9 and then divided the result by 3, giving an answer of 43. What would her answer have been had she worked the problem correctly?

Guide / Hint

Hint 1: Set up an equation for Cindy's incorrect calculation: .

Hint 2: Solve this equation to find the value of the original number .

Hint 3: Apply the teacher's correct instructions (subtract 3, then divide by 9) to the value of you found.

Solution

Step 1 (Represent Cindy's Calculation): Let the original number be . Cindy subtracted 9 from and then divided the result by 3, which gave an answer of 43. We write this as an equation:

Step 2 (Solve for the Original Number x): Multiply both sides by 3:

So the original number is 138.

Step 3 (Compute the Correct Answer): The teacher's original instruction was to subtract 3 from the number and then divide the result by 9. Applying this to :

Step 4 (Conclusion): Her answer would have been exactly 15.

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    2024 NMTC 2024 QII-55 - Olympiad Math Olympiad Question | Leminno