SOLUTION: Mr. Alan can finish a job in 3 hours by himself,And Mr. Brian can finish the job by himself in 5 hours. If Mr. Alan worked alone for 1 hour and Mr. Brian has to finish the job. How

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Question 251748: Mr. Alan can finish a job in 3 hours by himself,And Mr. Brian can finish the job by himself in 5 hours. If Mr. Alan worked alone for 1 hour and Mr. Brian has to finish the job. How long will it take him to finish the job by himself. Please write an equation.
Answer by richwmiller(17219) (Show Source):
You can put this solution on YOUR website!
It took me awhile in school to understand these work problems.
The key is finding what part of the job is done in a specific amount of time such as one hour, one day or one week.
Alan does 1/3 of the job in one hour
Brian does 1/5 of the job in one hour
Practically speaking, Brian will not really gain that hour that Alan worked since it will take that amount of time to find out what he did and be sure that the work Alan did was ok. And since he is a much slower worker, he probably doesn't know what he is doing!
So after one hour Alan did 1/3 of the job and skipped out.
So technically 2/3 of the job remain to be done
1/5t=2/3
--------t=10/3=3 1/3 hours ---------------
which is a savings of 1 2/3
This wasn't asked but the normal work problem asks how fast they can finish the job together.
and that would be t/3+t/5=1
we set it equal to one job
in our problem we set it equal to 2/3 since Alan had done 1/3 of the job.
t=15/8=1.875 hours
which sounds right since Alan can do the whole job alone in 3 hours.