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It takes 20 minutes for 5people to paint 5 walls. How many minutes does it take 9 people to paint 9walls?

 Jul 31, 2020
 #1
avatar+891 
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That would still take 20 minutes.  

 Jul 31, 2020
 #2
avatar+781 
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The equation for amount of work done is w=rth, where w represents the work done, r the rate, t the time, and h the number of people or things doing work.

 

So with the first sentence we have 5=r(20)(5), which simplifies to 5=100r, so r=1/20. Now we substitute this into the equation for our second sentence.

 

9=(1/20)(t)(9)

9=9/20t

t=20 minutes.

 Jul 31, 2020
 #3
avatar+26767 
0

People - hours per wall   =   5 p 1/3 hr / 5 w =  5/15  p-h / w

 

5 p- h / 15    *  9 w  /  9 =   5/15 hr = 20 min

 Jul 31, 2020

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