Two pipes P and Q, when opened alone can fill the tank in 20 and 30 hours respectively. If both pipes are opened together, then in how many hours will the tank be filled?
A buys an article for Rs.900 and sells it to B at a profit of 25%. B sells it to C, who sells it for Rs.1,350, at a loss of 10%. What profit percent (to the nearest integer) did B make?