Difficulty: Medium
Correct Answer: 64 days
Explanation:
Introduction / Context:
Use A’s solo time and the joint time to infer B’s rate, then apply it to the remaining fraction after the initial collaboration.
Given Data / Assumptions:
Concept / Approach:
Compute initial completed portion, then divide the remainder by B’s rate.
Step-by-Step Solution:
Work in first 8 days = 8 * (1/24) = 1/3.Remaining work = 1 − 1/3 = 2/3.B alone time = (2/3) / (1/96) = 64 days.
Verification / Alternative check:
Rough check: B is slow (96 days alone), so 2/3 of the job indeed needs about 64 days.
Why Other Options Are Wrong:
16, 32, 48, and 40 days misapply either the initial 8-day contribution or B’s rate.
Common Pitfalls:
Subtracting times rather than rates; ignoring that only 1/3 was done initially.
Final Answer:
64 days
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