Difficulty: Easy
Correct Answer: 33/7 days
Explanation:
Introduction / Context:
We must sum three rates and invert to get total time. These numbers are chosen so the result is a tidy fraction in simplest form, a common testing style.
Given Data / Assumptions:
Concept / Approach:
Combined rate r = 1/24 + 1/6 + 1/12. Total time = 1/r.
Step-by-Step Solution:
Common denominator 24: r = 1/24 + 4/24 + 2/24 = 7/24.Time = 1 / (7/24) = 24/7 days = 3 3/7 days = 33/7 days.
Verification / Alternative check:
Decimal: 24/7 ≈ 3.4286, between B’s 6 and C’s 12 when combined with A’s slower rate.
Why Other Options Are Wrong:
43/7, 4, 3, or 24/7 (if misread) don’t match the exact 24/7.
Common Pitfalls:
Arithmetic errors in fraction addition or misinterpreting 24/7 as an option separate from 33/7.
Final Answer:
33/7 days
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