SOLUTION: 9 men took 20 hours to paint a house. If all the men work at the same rate, how many hours would 15 men take to complete painting the house?

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Question 542430: 9 men took 20 hours to paint a house. If all the men work at the same rate, how many hours would 15 men take to complete painting the house?
Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!
9 men take 20 hours to paint a house. If all the men work at the same rate, how many hours would 15 men take to complete painting the house?

9 men and 15 men have a common factor of 3, so let's look at how
long 3 men would take, which would be 3 times as long.  Therefore

3 men would take 60 hours to paint a house.

Therefore since 15 is 5 times as many men as 3, those 15 men would 
take only one-fifth as long to paint a house as only 3 men would take.
One-fifth of 60 is 12.  Therefore

15 men would take 12 hours to paint a house.

Edwin