Advantage of duality
It avoids the necessity for adding surplus or artificial variables and solve the problem quickly. In economies, duality is useful in the formulation of the input and output systems. The dual variables provide an important economic interpretation of the final solution of an LP problem.
It is quite useful when investigating changes in the parameters of an LP problem.
Duality is used to solve the LP problem by the simplex method in which the initial solution is infeasible.