Difficulty: Medium
Correct Answer: 6 days
Explanation:
Introduction / Context:Different categories of workers often have different speeds. Convert each category to a per-person daily rate, add rates to get a team rate, and then compute time = work / rate. The unitary-method approach keeps the arithmetic clean and scalable.
Given Data / Assumptions:
Concept / Approach:Team rate = sum of individual rates, then time = 1 / (team rate). Be precise with fractions to avoid compounding rounding errors.
Step-by-Step Solution:
Men: 10 * (1/96) = 10/96 = 5/48 Women: 4 * (1/192) = 4/192 = 1/48 Children: 10 * (1/240) = 1/24 Team rate = 5/48 + 1/48 + 1/24 = 6/48 + 2/48 = 8/48 = 1/6 job/day Time = 1 / (1/6) = 6 daysVerification / Alternative check:Since the combined rate is exactly 1/6 job/day, finishing in 6 days is exact (no rounding).
Why Other Options Are Wrong:5, 7, 8, 10 days contradict the exact combined-rate computation 1/6 job/day.
Common Pitfalls:Adding times instead of rates, or using proportional reasoning on days rather than on daily work rates leads to wrong results.
Final Answer:6 days
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