This document discusses multiple projects and constraints in project management. It covers constraints like project dependence, capital rationing, and project indivisibility that must be considered when evaluating multiple projects. Mathematical programming techniques like linear programming can be used to determine the optimal combination of projects under these constraints. Linear programming formulates the project selection problem with an objective function to maximize value and constraint equations for limited resources and project interdependencies. The optimal solution selects the feasible combination of projects with the highest value.