SOLUTION: Tom takes 9 hours to do a job. sara takes 10 hours to do the same job. How long would it take if they worked together?

Question 1130738: Tom takes 9 hours to do a job. sara takes 10 hours to do the same job. How long would it take if they worked together?
Found 2 solutions by ankor@dixie-net.com, Alan3354:
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Tom takes 9 hours to do a job.
sara takes 10 hours to do the same job.
How long would it take if they worked together?
:
let t = time required when working together
let the completed job = 1
Each will do a fraction of the job, the two fractions add up to 1
+ } = 1
multiply equation by 90 and cancel the denominators
10t + 9t = 90
19t = 90
t = 90/19
t = 4.737 hrs or 4 + .737(60) = 4 hrs 44 min
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Tom takes 9 hours to do a job. sara takes 10 hours to do the same job. How long would it take if they worked together?
------------
There's a "shortcut" for parallel work, flow, resistance, etc.
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9*10/(9+10) hours for this one.
= 90/19 hours

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