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Question 16300: a job can be done by 11 workers in 15 days. five workers started the job. at the beginning of the 6th day, 4 more workers reinforced the job. find the total number of days it took them to finished the job?
Answer by rapaljer(4671)   (Show Source):
You can put this solution on YOUR website! I've never solved a problem like this before, but let me take a shot at it. Maybe you would like to repost the question, and get a second opinion from someone else.
The way I look at it, if the job can be done by 11 workers in 15 days, then it will take a total of 165 worker-days to get the job done. In other words if one person is working alone it will take a total of 165 days to do it. If 5 people work on it, it will be done in 165/5 = 33 days.
So, if 5 worker start the job and work for 5 days, they will get 25 worker-days worth of the job done, leaving 140 worker-days left after the first 5 days are accomplished. Now, 4 more workers come in to reinforce the job, so there are 9 workers working from this point on. So, divide 140 worker-days by 9 workers which gives you 15.55 days. In other words they will finish on the 16th day plus the first 5 days of work. I would say that they finish on the 21st day from the day they started.
R^2 at SCC
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