A can do a piece of work in 10 days and B alone can do it in 20 days. How much time will both take to finish the work ?  Choose the correct choice.
A) A)5.333 B) B)6 C) C)6.666 D) D)8.333 E) E)9
This question can be solved by different methods. We need to conserve time in exams so solving this problem using equations is the good idea.   Time taken to finish the job = XY / (X + Y)   = 10 x 20 / (10 + 20)   = 200 / 30   = 6.666 days   Answer: 6.666
<result>C</result>
A can do a piece of work in 10 days and B alone can do it in 20 days. How much time will both take to finish the work ?