Abstract Purpose – For extending the common definitions and concepts of grey system theory to the optimization subject, a dual problem is proposed for the primal grey linear programming problem. Design/methodology/approach – The authors discuss the solution concepts of primal and dual of grey linear programming problems without converting them to classical linear programming problems.Anumerical example is provided to illustrate the theory developed. Findings – By using arithmetic operations between interval grey numbers, the authors prove the complementary slackness theorem for grey linear programming problem and the associated dual problem. Originality/value – Complementary slackness theorem for grey linear programming is first presented and proven. After that, a dual simplex method in grey environment is introduced and then some useful concepts are presented.
