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

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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