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Question 522921: 4 people can paint 3 walls in 36 minutes.
How many minutes will it take for 5 people to paint 10 walls? Round to the nearest minute.
Please show me how to arrive at the answer.
Answer by oberobic(2304)   (Show Source):
You can put this solution on YOUR website! Really problems like this are always fraction problems.
What we try to find is the fractions that are multiplied to do "1 whole job".
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The crew of 4 people can complete 3 walls in 36 minutes.
The crew can paint 1 wall in 1/3 * 36 = 12 minutes.
The crew does 1/12 of a wall per minute.
Each person is 1/4 of the crew, so each person does 1/4*1/12 = 1/48 of a wall per minute.
So, we know know that one person can do 1/48 of a wall per minute.
5 people can do 5*1/48 = 5/48 of a wall per minute.
So, in 48 minutes they can do 48 min * 5/48 wall/min = 5 walls.
To do 10 walls will take: 2 * 48 min = 96 min.
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We found that "1 whole wall" takes 12 minutes.
In turn, this means they can do 1/12 of the job per minute.
1/12 per minute * 12 minutes = 1 wall
A crew of 5 is 1.25 more than a crew of 4, so they can paint 25% faster per minute.
(5-4)/4 = 1/4 = .25
That means they can do 1 1/4 or 1.25 wall per 12 minutes.
Instead of 12 minutes per wall, they can do 1 wall in 12/1.25 = 9.6 min.
To do 10 walls will take 10*9.6 = 96 minutes.
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