Question

It takes 6 technicians a total of 10 hours to build a new server from direct computer, with each working at the same rate. If six technicians start to build the server at 11:00 am, and one technician per hour is added beginning at 5:00 pm, at what time will the server be completed?

• A. 6:40 pm
• B. 7:00 pm
• C. 7:20 pm
• D. 8:00 pm

Hint:

Break variable workforce problems into hourly segments, summing work done until total = 1.

Answer 1

The Correct Option is D

Work rate of each technician = \(\frac{1}{60}\) of the job/hour (since \(6\) techs complete in \(10\) hrs → \(60\) tech-hours per job).
From 11:00 am to 5:00 pm: Work done = \(6 \times 6 \times \frac{1}{60} = 0.6\) of the job.
Remaining = \(0.4\).
At 5:00–6:00 pm: 7 techs → \(7/60 \approx 0.1167\) → remaining \(0.2833\).
At 6:00–7:00 pm: 8 techs → \(8/60 \approx 0.1333\) → remaining \(0.15\).
At 7:00 pm: 9 techs → time needed = \(0.15 / (9/60) = 1\) hour.
Finish time = **8:00 pm**.