Question

Worker A takes 12 hours to do a job, worker B takes 6 hours to do the same job. How long should it take both A and B, working together?

Answer 1

Answer:

Assume the work will be finished in x hours. For the independent work to fulfill, A and B should not work simulatneusly on the same time. In an hour A (alone) will finish 1/8 part of x, while B finish it 1/10 part of x. Since they need to work alone B should work after A finished the work. A will work in the first hour. Then A stops working, and B takes over for next hour. Within 2 hours together they will finish the work in (1/8 x + 1/10 x) = 18/80 x within 2 hours. So for an hour they together will finish 9/40 x . So x = 40/9 hours = 4 hours, 6 minutes and 40 seconds.

Answer 2

Answer:

72÷18=4hr this is answer