SOLUTION: peter can finish an accounting work in 8 hours. david can finish the same work in 6 hours. After 2 hours of working together, peter left david for lunch and david finished the job.

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Question 985198: peter can finish an accounting work in 8 hours. david can finish the same work in 6 hours. After 2 hours of working together, peter left david for lunch and david finished the job. how long does it take david to finish the job?
Answer by srinivas.g(540) About Me  (Show Source):
You can put this solution on YOUR website!
Peter can finish an accounting work in 8 hours..
let total work be 1 unit
In 1 Hour, amount of work done by peter = 1/8
david can finish the same work in 6 hours
In 1 Hour, amount of work done by David = 1/6
In 1 Hour, amount of work done by both peter and david together = %281%2F8%29%2B%281%2F6%29
=%286%2B8%29%2F48
=14%2F48
=7%2F24
In 2 hours, amount of work done by both together =2%2A%287%2F24%29
=7%2F12
after 2 hours , peter left
amount of work remaining = 1-%287%2F12%29
=+5%2F12
this remaining work completed by David alone
David finish total work alone in 8 hours
david finish 5%2F12 of the work in = %285%2F12%29%2A8
=10%2F3
=3.33 Hours
= 3 hours +0.33 hour
= 3 hours+0.33*60 min
= 3 hours 20 minutes
David finish the remaining work in 3 hours 20 min