A shopkeeper bought 80 kg of rice at a discount of 10%. Besides 1 kg rice was offered free to him on the purchase of every 20 kg rice. If he sells the rice at the marked price, his profit percentage will be:
A pump can fill a tank with water in 1 hour. Because of a leak, it took \(1{1\over3}\) hours to fill the tank. In how many hours can the leak alone drain all the water of the tank when it is full?