SOLUTION: if rob sarah and George can complete a job in 12 days and rob can work 6 times faster than sarah and 3 times faster than George...how long would it take sarah to complete the job h

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Question 892275: if rob sarah and George can complete a job in 12 days and rob can work 6 times faster than sarah and 3 times faster than George...how long would it take sarah to complete the job herself?
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
RT=J for rate time job.
Uniform rates for job or task completion.
Rate is in units of jobs per days.

Let d = time for Rob to do 1 job;
Rob, 1/d
George, 1/(3d)
Rob&George, 1/12
Sarah, 1/(6d)

Think very carefully about those rate expressions and how they conform to the description before continuing.

-----

The combined work rate for Rob and George is the sum of their rates.
highlight_green%281%2Fd%2B1%2F%283d%29=1%2F12%29
3%2F%283d%29%2B1%2F%283d%29=1%2F12
4%2F%283d%29=1%2F12
3d%2F4=12
3d=36
highlight%28d=12%29

With d now known, the rates for Rob and George can be evaluated. The time for Sarah to do 1 job is highlight%286d=highlight%2872%29%29 days.

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

if rob sarah and George can complete a job in 12 days and rob can work 6 times faster than sarah and 3 times faster than George...how long would it take sarah to complete the job herself?


Sarah can do job in: highlight_green%28108%29 days

You can do the check!! 



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