Question 890104
x people can complete 1 project in y hours.
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1 person will complete 1/x project in y hours. 
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The project was divided (keyword here) evenly in x parts for x people. 1 project, divided in x parts, it is 1/x.
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If you're still unsure, replace x with a number and see that it works. If x=4, there are 4 people doing exactly 1/4 of the project each.