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Characteristics of the dual problem:

1. For any linear programming model called primal model, there exists a companion model called the dual model.

2. The number of constraints in the primal model equals the number of variables in the dual model.

3. The number of variables in the primal problem equals the number of constraints in the dual model.

4. If the primal model is a maximization problem then the dual model will be of the form less than or equal to, “≤” while the restrictions in the dual problem will be of the form-greater than or equal to, “≥”.

5. The solution of the prima; model yields the solution of the dual model. Also, an optimal simplex table for the dual model yields the optimal solution to the primal model. Further, the objective functions of the two optimal tables will have identical values.

6. Dual of the prima’s dual problem is the primal problem itself.

7. Feasible solutions to a primal and dual problem are both optimal if the complementary slackness conditions hold, that is, (value of a primal variable) x (value of the corresponding dual surplus variable) = 0 or (value of a primal slack variable) x (value of the corresponding dual variable) = 0.

If this relationship does not hold, than either the primal solution or the dual solution or both are no optimal.

8. If the primal problem has no optimal solution because of infeasibility, then the dual problem will have no optimal solution because of unboundedness.

9. If the primal has no optimal solution because of unboundedness, then the dual will have no optimal solution because of infeasibility.

1. For any linear programming model called primal model, there exists a companion model called the dual model.

2. The number of constraints in the primal model equals the number of variables in the dual model.

3. The number of variables in the primal problem equals the number of constraints in the dual model.

4. If the primal model is a maximization problem then the dual model will be of the form less than or equal to, “≤” while the restrictions in the dual problem will be of the form-greater than or equal to, “≥”.

5. The solution of the prima; model yields the solution of the dual model. Also, an optimal simplex table for the dual model yields the optimal solution to the primal model. Further, the objective functions of the two optimal tables will have identical values.

6. Dual of the prima’s dual problem is the primal problem itself.

7. Feasible solutions to a primal and dual problem are both optimal if the complementary slackness conditions hold, that is, (value of a primal variable) x (value of the corresponding dual surplus variable) = 0 or (value of a primal slack variable) x (value of the corresponding dual variable) = 0.

If this relationship does not hold, than either the primal solution or the dual solution or both are no optimal.

8. If the primal problem has no optimal solution because of infeasibility, then the dual problem will have no optimal solution because of unboundedness.

9. If the primal has no optimal solution because of unboundedness, then the dual will have no optimal solution because of infeasibility.