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As a punishment for something naughty that we did, my little brother and I have to whitewash both sides of a fence. We start at the same time, and we each work at a constant rate. If we each whitewash one side, I'll finish in 2 hours and my brother will finish in 3 hours. But I'm a nice kid, so after I finish my side, I go around to the other side and help my brother finish his side. From the time I start helping him, how many minutes does it take us to finish the job?

Guest May 6, 2017
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As a punishment for something naughty that we did, my little brother and I have to whitewash both sides of a fence. We start at the same time, and we each work at a constant rate. If we each whitewash one side, I'll finish in 2 hours and my brother will finish in 3 hours. But I'm a nice kid, so after I finish my side, I go around to the other side and help my brother finish his side. From the time I start helping him, how many minutes does it take us to finish the job?

 

Well....you can paint 1/2 of the fence on your side in one hour and your brother can paint 1/3 of the fence on his side in one hour.....so...together......you both can paint (1/2) + (1/3)  =  5/6 of the fence on either side in one hour

 

So....after 2 hours......your brother has painted  2 (1/3)  = 2/3 of the fence on his side and there is 1/3 left to paint

 

So

 

Work left / Rate Per Hour  = Time to finish

 

(1/3) / (5/6)  =

 

(1/3) (6/5)  =

 

6/15  hrs  =

 

2/5 hrs   =

 

24 minutes  

 

P.S. -   have you and your brother ever read "Tom Sawyer??"

 

cool cool cool

CPhill  May 6, 2017

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