I have been struggling with this kind of problem ever since I can analyze the rate-in and rate-out with other brine problems. It is fine for me to show up the differential equation beyond your solution.
A tank contains 400 liters of brine. Twelve (12) liters of brine, each containing 2.50 kg of dissolved salt enter the tank per minute and the mixture kept uniform by stirring, leaves at the rate of 8 liters per minute. If the concentration is to be 2.00 kg per liter at the end of one hour, how many kgs of salt were originally present in the tank?
As what I have understood, my rate-in would probably 2.50 kg/min which is the given. However, I don't know much about the rate-out because of how to formulate the concentration of the tank.