Finding Constraints in Linear Programming

This question was posted by Siboniso

How do we find constraints in linear programming?

Thanks for the question Siboniso,

There are two different kinds of questions that involve finding constraints.

The first comes directly from the diagram.

In this case it is a simple matter of finding the equation of the straight line using the x and y-intercepts to find the gradient and c value (y-intercept). Then rearrange the question so that the x’s and y’s are on one side and the constant is on the other. Look at your feasible region. If it lies below your line then the the x and y must be < or = to the constant. If the feasible region lies above the line then your x and y must be > or = to the constant.

The second comes from analysing the information given to you.

You need to make sure that you group like with like. By this I mean that sometimes the questions will be phrased over several statements – look at what the make x and y and then look at what is said about x and y. For example – they might only give you x in one statement, y in the next statement and all the constants in the last sentence. Make sure that you pay attention to keywords and ratios. Think about it logically and remember your crocodile mouths 🙂

Check out our students area under latest chapters – grade 12 chapter 6 – linear programming for a more in depth study of linear programming and lots of practice.

Good luck 🙂

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