Worker A takes 10 hours to do a job. Worker B takes 12 hours to do the same job. How long it take both A & B, working together but independently, to do the same job?
Choose the correct choice from the following answers:
A) 40 days  B) 40/9 days  C) 60/11 days  D) 30/9 days  E) 60/9 days
A's one hour work = 1/10.   B's one hour work = 1/12.   (A+B)'s one hour work = 1/10+1/12 = 11/60.   Both A &amp; B can finish the work in 60/11 days   60/11 days
<result>C</result>
Worker A takes 10 hours to do a job. Worker B takes 12 hours to do the same job. How long it take both A & B, working together but independently, to do the same job?