SOLUTION: sam can complete a job in 20 minutes working alone. if he joined by the twins jim and tim who work at the same rate ,they can complete the job in 10 minutes. how long would it take

Question 323323: sam can complete a job in 20 minutes working alone. if he joined by the twins jim and tim who work at the same rate ,they can complete the job in 10 minutes. how long would it take for only the twins to work together to complete the job ?
A 40 min b 30 min c 20 min D 15 min
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
sam can complete a job in 20 minutes working alone.
if he joined by the twins jim and tim who work at the same rate, they can complete the job in 10 minutes.
how long would it take for only the twins to work together to complete the job ?
:
Let x = time required when the twins do the job alone
:
Let the completed job = 1
:
+ = 1
Reduce fraction
+ = 1
multiply by 2x, results
1x + 10(2) = 2x
20 = 2x - x
x = 20 min

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