Hi All,
These types of 'Work' questions can be solved in a couple of different ways (depending on how you want to 'organize' the rate information). It can often help to think in terms of the number of worker-hours required to complete the job.
The Qualified Worker takes 5 hours to complete a job, so the job requires 5 Worker-hours of effort to be finished.
The Qualified Worker can complete 1 Worker-hour per hour.
Each of the two apprentices can complete 3/4 of a Worker-hour per hour.
Each of the two trainees can complete 1/5 of a Worker-hour per hour.
Total = 1 + 2(3/4) + 2(1/5) = 1 + 1.5 + .4 = 2.9 Worker-hours completed per hour by this group.
Since the job requires 5 Worker-hours of effort, the total time will be...
5/2.9 hours =
50/29 hours =
1 21/29 hours
21/29 is a little more than 2/3 (since 20/30 = 2/3). Thus, we're looking for an answer that is a little more than 1 2/3 hours. There's only one answer that matches....
Final Answer:
GMAT assassins aren't born, they're made,
Rich
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