Difficulty: Easy
Correct Answer: 5
Explanation:
Introduction / Context:
Here a four-digit number has one missing digit. You are told the exact quotient when dividing by 11. The task is to recover the unknown digit by reversing the division, a staple skill in number-system puzzles.
Given Data / Assumptions:
Concept / Approach:
If N / 11 = 233, then N = 233 * 11. Compute the product, then compare digits with the pattern 2?63 to read off the missing digit. This avoids long division and reduces computational effort.
Step-by-Step Solution:
Compute 233 * 11 = 233 * (10 + 1) = 2330 + 233 = 2563.Match 2563 with 2?63: clearly, ? = 5.Therefore the missing digit is 5.
Verification / Alternative check:
Divide 2563 by 11: 2563 / 11 = 233 exactly, confirming correctness and aligning with the given quotient.
Why Other Options Are Wrong:
Digits 4, 3, or 6 would produce 2463, 2363, or 2663, none of which are multiples of 11 equaling 233.
Common Pitfalls:
Trying to apply the alternating-sum test for divisibility by 11 to guess the digit, which can be slower than simply multiplying 233 * 11 for this exact quotient scenario.
Final Answer:
5
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