- Because of constraints like project dependencies, capital rationing, and project indivisibility, investment projects cannot be viewed in isolation. Two common approaches used to evaluate multiple projects are the method of ranking and mathematical programming. - The method of ranking ranks projects by their NPV, IRR or BCR but has problems like conflict in rankings between criteria and inability to handle project indivisibility. - Mathematical programming models like linear programming, integer linear programming and goal programming formulate the problem as an objective function subject to constraints, allowing complex project interdependencies and capital rationing to be incorporated.