Machine A working alone can complete a job in 10 hours. Machine B working alone can do the same job in 12 hours. How long will it take both machines working together at their respective constant rates to complete the job? Choose the correct choice from the following
A) 50/11 B) 60/11 C) 40/11 D) 47/11 E) 57/15
Machines ( A ) ( 60/11 ) (A+60/11)   ---Time - 10 - ( 12 ) -   ---Rate 12--- 10-- 22   --Work 120 --120 -120   A+60/11 = (120/22) = 60/11   60/11
<result>B</result>
Machine A working alone can complete a job in 10 hours. Machine B working alone can do the same job in 12 hours. How long will it take both machines working together at their respective constant rates to complete the job?