Difficulty: Medium
Correct Answer: 1001/3
Explanation:
Introduction / Context:
This product is crafted to telescope. Each factor uses consecutive odd integers in the fraction, enabling massive cancellation when expressed with a common pattern.
Given Data / Assumptions:
Concept / Approach:
Rewrite each factor: 2 − k/(k + 2) = (2(k + 2) − k)/(k + 2) = (k + 4)/(k + 2). This turns the entire product into a chain of ratios that cancel successively.
Step-by-Step Solution:
For k = 1: (k + 4)/(k + 2) = 5/3.For k = 3: 7/5. For k = 5: 9/7. … For k = 997: 1001/999.Product P = (5/3) × (7/5) × (9/7) × … × (1001/999).Everything cancels except the smallest denominator 3 and the largest numerator 1001.Hence P = 1001/3.
Verification / Alternative check:
Write out the first few and last few terms to see direct cancellation of intermediate numerators and denominators.
Why Other Options Are Wrong:
1001/999 and 999/1001 reflect partial cancellation; 5/1001 and 3/1001 invert endpoints incorrectly.
Common Pitfalls:
Losing the pattern of consecutive odds or not expressing each factor as (k + 4)/(k + 2) before multiplying.
Final Answer:
1001/3
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