A crew of 6 workers can install 240 linear feet of electrical conduit in 8 hours. If you need to install 900 linear feet and want to complete the work in 6 hours, how many workers do you need?
Correct Answer
C) 15 workers
Current rate: 240 LF ÷ (6 workers × 8 hours) = 5 LF per worker-hour. For 900 LF in 6 hours: 900 ÷ 6 = 150 LF per hour needed. 150 LF ÷ 5 LF per worker-hour = 30 worker-hours ÷ 6 hours = 5 workers per hour × 3 shifts = 15 workers.
Why This Is the Correct Answer
First, calculate the productivity rate: 240 LF ÷ (6 workers × 8 hours) = 5 LF per worker-hour. To install 900 LF in 6 hours requires 900 ÷ 6 = 150 LF per hour. Since each worker produces 5 LF per hour, you need 150 ÷ 5 = 30 worker-hours per hour, which means 15 workers working simultaneously for 6 hours.
Why the Other Options Are Wrong
Option A: 18 workers
18 workers would provide 18 × 5 = 90 LF per hour × 6 hours = 540 LF total, which is insufficient to complete the 900 LF required. This answer likely comes from miscalculating the required production rate or worker productivity.
Option B: 12 workers
12 workers would produce 12 × 5 = 60 LF per hour × 6 hours = 360 LF total, falling far short of the 900 LF requirement. This error typically results from incorrect unit conversions or misunderstanding the time constraint.
Option D: 20 workers
20 workers would produce 20 × 5 = 100 LF per hour × 6 hours = 600 LF total, which is still 300 LF short of the 900 LF target. This represents overestimating workforce needs without proper calculation verification.
Memory Technique
Remember 'Rate × Workers × Time = Total Work.' First find the rate per worker-hour, then work backwards from your target (900 LF in 6 hours) to find required workers.
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