Worker A takes 8 hours to do a job. Worker B takes 10 hours to do a job. How long should it take both A and B, working together to do same job.
Correct Answer : D.
In this type of questions, first we need to calculate 1 hours work, then their collective work as, A's 1 hour work is 1/8 B's 1 hour work is 1/10 (A+B)'s 1 hour work = 1/8 + 1/10 = 9/40 So both will finish the work in 40/9 hours =