Operations research
Cheat sheet
Formulating an LP model: the one-card revision
LP formulation on one card. Can you name all five parts first?
Quick check · tap an answer to continue
Lesson notes
Key points
- Decision variables: First define what you control, like x1 tonnes of ore A mined.
- Objective function: Write the linear goal to maximise profit or minimise cost, using the variables.
- Constraints: Each limited resource becomes a linear inequality, such as labour hours available.
- Non-negativity: Always add x1, x2 greater than or equal to zero; examiners deduct marks otherwise.
- Slack and surplus: Slack fills a less-than constraint; surplus is subtracted from a greater-than constraint.
Takeaway: Variables, objective, constraints, non-negativity: never skip the last.
Quick check: What variable is subtracted to turn a ≥ constraint into an equation?
- Slack variable
- Surplus variable
- Decision variable
Surplus measures the excess above a minimum, so it is subtracted.
Lessons like this, for your syllabus.
Short narrated study videos written for your course, level and exam. Free to start.
Get lessons for your own syllabus