Surplus variables

Surplus variables

In a linear programming model when a structural constraint is in the “Greater  than or equal to” form a non-negative variable is deducted to the left hand side to convert inequality into equation, then these variables are called as slack variables.

For example: 3X + 5Y ≤ 100

Or, 3X - S₁ + 5Y - S₂ = 100.

Here S₁ and S₂ are Surplus variables.