Mixing Problems in Calculus: Salt in Water Tank

A tank contains 20 kg of salt dissolved in 5000 L of water. Brine that contains 0.03 kg of salt per liter of water enters the tank at a rate of 25 L/min. The solution is kept thoroughly mixed and drains from the tank at the same rate. How much salt will there be in the tank after half an hour? This is a typical mixing problem that students often see in Calculus 2 classes. There is also another kind of mixing problem that involves percentages. I will cover this type of mixing problem in the next video. There are three formulas that you need to know. They will result in a separable differential equation that you can easily solve.