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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 4 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?

 Jun 20, 2022
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When you finish your side, your brother will  still have two hours left.

 

In one hour you can  finish  1/2  of a side and your  brother can  fininsh 1/4 of aside

 

So...in one hour   working together  you  both  can  finish  1/2 + 1/4  = 3/4  of a side

 

Take the reciprocal of this =  4/3 

 

So....it will  take  4/3 of an hour  =  1hr 20 min =  80  min to finish once you start helping him

 

 

cool cool cool

 Jun 20, 2022

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