Ink is fed into a glass jar with an overflow valve at a consent rate.
The water and ink are being continually mixed and the excess is allowed to drain out of the overflow valve so as to keep the amount of liquid in the glass jar constant. A differential equation modeling the process is derived and the solution is given. Students are asked to verify the solution and to graph it as a preliminary to the experiment. The experiment consists of the students pouring the ink into the glass jar by hand. They collect data on how much ink is present by determining how clear the mixture is.