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Kevin, can clean a stadium in 5 hours working alone. Chris, can clean the same...

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robertsonm | eNotes Newbie

Posted June 12, 2013 at 9:27 PM via web

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Kevin, can clean a stadium in 5 hours working alone. Chris, can clean the same stadium in 3 hours. How long will it take for both Kevin and Chris to clean the stadium if they work together?

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llltkl | College Teacher | Valedictorian

Posted June 13, 2013 at 12:50 AM (Answer #1)

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Kevin, can clean the entire stadium in 5 hours working alone. Therefore, in 1 hour and working alone, Kevin can do 1/5 portion of the total cleaning job.

Similarly, Chris can clean the entire stadium in 3 hours working alone. Therefore, in 1 hour and working alone, Chris can do 1/3 portion of the total cleaning job.

Working together, in 1 hour, they can do (1/5+1/3) = 8/15 portion of the total cleaning job.

Therefore, working together they would complete the entire cleaning job in 1/(8/15) = 15/8 hours = 1.875 hours = 1 hour and 52.5 minutes.

So, it would take 1 hour and 52.5 minutes for both Kevin and Chris to clean the stadium if they work together.

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