Pramod can paint a wall red in 12 hours while Brajen can whitewash the wall completely in 16 hrs. If Pramod and Brajen work alternately for an hour each starting when the wall has just cement on it till when it is completely painted red, how many hours will it take to paint the entire wall red?
Anil can do a piece of work in 14 days which Rohit can do in 21 days. They worked together for few days after which Anil left. If Rohit worked alone for 3 days, find the total number of days it took to complete the whole work.