Final answer:
If 15 workers can complete a job in 8 hours, it would take 5 workers 12 hours to complete half of the job, based on the calculation of work units and the rate of work.
Step-by-step explanation:
If 15 workers can do a job in 8 hours, we first determine the total amount of work done which we can call work units. In this case, 15 workers × 8 hours = 120 work units (since each worker contributes 8 hours of work). Now, if we have 5 workers and we want to do half the job, that translates to 60 work units (half of 120 work units). Since one worker contributes 1 unit of work per hour, 5 workers would contribute 5 units of work per hour.
To find out how many hours it would take for 5 workers to complete 60 units of work, we divide the total amount of work by the rate at which 5 workers can complete the work: 60 work units ÷ 5 workers = 12 hours. Therefore, it would take 5 workers 12 hours to complete half the job.