'A' and ' B ' can do a piece of work in 25 days and 30 days respectively. Both start the work together but 'A' leaves the work 8 days before its completion. Find the time in which the work is finished.
A person travels for 5 hours at the speed of 40 kmh"1 and for 6 hours at the speed of 50 kmh'1 . At the end of it, he finds that he has covered 1/2 of the total distance. At what average speed should he travel to cover the remaining distance in 10 hours ?