SOLUTION: It takes 9 people 9 days to finish a project if they work 9 hours a day. If only 8 people work only 8 hours a day, how long would it take?

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Question 358986: It takes 9 people 9 days to finish a project if they work 9 hours a day. If only 8 people work only 8 hours a day, how long would it take?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
This is a problem on inverse variation. The no. of days D to finish the work is inversely proportional to the number of hours worked h and the number of people p working. Thus D+=+k%2F%28p%2Ah%29, where k is a proportionality constant.
9+=+k%2F%289%2A9%29+=+k%2F9%5E2, so that k+=+9%5E3+=+729.
Then D+=+729%2F%288%2A8%29+=+729%2F64+=+11.39 hours.