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Question 15893: Dave can do the job in 8 hours. after working for one hour, he is joined by howard and both finished the job 2 more hours. how long will it take Howard to do the job alone?
Answer by Earlsdon(6294)   (Show Source):
You can put this solution on YOUR website! Let's start by finding the hourly rates at which Dave and Dave & Howard work.
If Dave can do the entire job in 8 hours, then he can do 1/8 of the job in 1 hour.
After dave has worked for 1 hour, he has completed 1/8 of the job, leaving 7/8 to be finished by Dave & Howard in 2 hours.
So, if Dave & Howard can do 7/8 of the job in 2 hours, then they can do 7/16 (just half of 7/8) of the job in 1 hour.
Now we'll subtract Dave's rate from Dave & Howard's combined rate leaving us with Howard's hourly rate.
H&D - D = H
7/16 - 1/8 or 7/16 - 2/16 = 5/16
Howard can do 5/16 of the job in 1 hour, therefore, it will take him 16/5 hours to do the entire job alone.
16/5 hours = 3 1/5 hours = 3 hours and 12 minutes.
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