Operations research
This or that
Slack or surplus? Four OR pairs to test
Do you really know the difference? Answer before I do.
Quick check · tap an answer to continue
Lesson notes
Key points
- Slack / Surplus: Slack is added to ≤ constraints; surplus is subtracted from ≥ constraints.
- Basic / Non-basic: Basic variables can be nonzero in the solution; non-basic variables are set to zero.
- Entering / Leaving: Entering comes from the objective row; leaving comes from the minimum ratio test.
- Degenerate / Unbounded: Degenerate means a basic variable equals zero; unbounded means the objective grows forever.
Takeaway: Slack fills ≤, surplus trims ≥; ratio test picks who leaves.
Quick check: Ties in the Simplex minimum ratio test usually lead to what?
- An unbounded solution
- A degenerate solution
- An infeasible solution
A tied ratio leaves a basic variable at zero, which is degeneracy.
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