How can linear programming be used in the real world?
Linear programming is a mathematical technique for analyzing systems of equations whose variable interact with each other.
Many "real world" applications exist, as it can be applied to scientific studies, business and even social interactions. It's primary function is to determine the model parameters of the variables necessary to optimize a particular characteristic.
It can also be used simply to model the effects of a change in one or more variables on the others in the system. To be effective, it does need a fairly good predictive mathematical model of each of the variables, and in particular with respect to their interactions on each other.
For example, plant growth depends on the amount of available moisture, which depends on both ground water and rain, each of which in turn is dependent on other variables like temperature and sunlight.
A linear program to determine the variables needed for optimum plant growth would need to include the equations related to the moisture, as well as those related to nutrients, predators, and so on. If a sub-model equation is inaccurate, it will affect the accuracy of the entire model, wherever it is a factor.
This is one reason that "Climate Modeling" is MUCH more difficult and imprecise than most of the study "outcomes" would imply!