In teaching the use of mathematical modeling in the Industrial Engineering area, one is often faced with situations where the decision variable is restricted to a few discrete values. In such circumstances I have found it pedagogically advantageous to use the concept of indifference curves, i.e., curves in a suitable two-dimensional space showing under what conditions we are indifferent between neighboring values of the decision variable. This note illustrates the use of indifference curves in a particular inventory control model.