<PRE><B>Question 919064</B>
working together two servicemen can clean a swimming pool in 6 hours. If both of them worked together for the first three hours, and the first stopped for one reason or another, it will require the second 4 hours more to rub clean the pool. How long does it take each of them separately to do the job?
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let x=amt of time 2nd can finish the separately
1/x=his work rate
let y=amt of time 1st can finish the separately
1/y=his work rate
6 hrs=amt of time 1st and 2nd working together can finish the job
1/6=their work rate
..
3*(1/6)+4*(1/x)=1 (100% completion of job)
3/6+4/x=1
4/x=1-3/6=1/2
x=8
..
working together:
1/y+1/x=1/6
1/y=1/6-1/x
1/y=1/6-1/8=4/24-3/24=1/24
y=24
..
amt of time 2nd can finish the job separately=8 hrs
amt of time 1st can finish the job separately=24 hrs</PRE>