SOLUTION: Jake can complete a job in 5 hours while Jerry can complete the same job in 3 hours. How long would it take to complete the job if Jake starts the job 2 hours before Jerry joins hi

Algebra ->  Rate-of-work-word-problems -> SOLUTION: Jake can complete a job in 5 hours while Jerry can complete the same job in 3 hours. How long would it take to complete the job if Jake starts the job 2 hours before Jerry joins hi      Log On


   

Question 23027: Jake can complete a job in 5 hours while Jerry can complete the same job in 3 hours. How long would it take to complete the job if Jake starts the job 2 hours before Jerry joins him?
Answer by deepikabansal(5) About Me  (Show Source):
You can put this solution on YOUR website!
Solution: As given in problem
In 5 hours Jake can do 1 job
=>In 1 hour he can do 1/5 job
similarly
in 3 hours Jerry can do 1 job
=> in 1 hour she can do 1/3 job
so together in 1 hour they can do (1/5) +(1/3)job
=(3+5)/15job
=8/15job Now, jack has done 2 hours job alone before she joins him.
so job done by jack alone=2/5job
job remaining=1-(2/5)=3/5
this 3/5job has to be done by both of them
by unitary method,
as 8/15 job is done in 1 hour
1 job is done in 15/8 hours
3/5 job is done in (15/8)*(3/5)hours
9/8 hours
ie 1hour7.5minutes.
so they will complete job in 1hour and 7.5 minutes