Questions tagged [linear-programming]

Questions on linear programming, the optimization of a linear function subject to linear constraints.

A linear programming problem may be defined as the problem of maximizing or minimizing a linear function subject to linear constraints. The constraints may be equalities or inequalities.

Linear programs are problems that can be expressed in canonical form as \begin{align}\max\quad&c^\top x\\\text{s.t.}\quad& Ax\le b\\\quad& x\ge 0\end{align} where $x$ represents the vector of variables (to be determined), $c$ and $b$ are vectors of (known) coefficients, $A$ is a (known) matrix of coefficients, and ${\displaystyle (\cdot )^{\top}}$ is the matrix transpose.

The expression to be maximized or minimized is called the objective function ($c^{\top}x$ in this case).

The inequalities $Ax \le b$ and $x \ge 0$ are the constraints which specify a convex polytope over which the objective function is to be optimized. The inequality $x \ge 0$ is called non-negativity constraints and are often found in linear programming problems. The other inequality $Ax \le b$ is called the main constraints.

Applications:

Linear programming can be applied to various fields of study. It is widely used in mathematics, and to a lesser extent in business, economics, and for some engineering problems. Industries that use linear programming models include transportation, energy, telecommunications, and manufacturing. It has proven useful in modeling diverse types of problems in planning, routing, scheduling, assignment, and design.

References:

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Unbounded solution of LPP

In connection with LPP, what is meant by 'unbounded solution' and 'unbounded objective function'? Are they same or they are distinct concepts?
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Graphical solution of lpp

I need to solve the following LPP using graphical method Min $z=-2x_1+x_2$ subject to $x_1+x_2 \geq 6$, $3x_1+2x_2 \geq 16$, $x_2 \leq 9$, $x_1, x_2 \geq 0$ The common feasible region is unbounded. I am not sure whether the solution is also…
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Solution of LPP by graphical method

I need to solve the following LPP using graphical method Min $z=4x_1+x_2$ subject to $2x_1+x_2 \geq 2$, $x_1+3x_2 \leq 4$, $x_2 \leq 4$, $x_1, x_2 \geq 0$ But I am not finding any common feasible region. Particularly from the figure we see that…
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How to initialise a linear program?

Good morning! I'm absolutely new to linear programing since this year, yet I'm struggling to understand and learn. I was given during my lecture that to chose the initial vertice we had to determine a vertice of $U$ if it is not empty or to show…
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Linear Programming #3

A small tailors’ company wants to use at least 130 yards of fabric to sew evening skirts and dresses. A dress requires 4 yards of fabric and the production of a skirt will need 3 yards. Research shows that they will be able to sell at most three…
Dan
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Linear Programming Word Problems (#2)

A small tailors’ company wants to use at least 130 yards of fabric to sew evening skirts and dresses. A dress requires 4 yards of fabric and the production of a skirt will need 3 yards. Research shows that they will be able to sell at most three…
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general solution for Linear Programming problem

Given a generic LP with a single constraint: maximize $c_1x_1 + c_2x_2 +.... c_nx_n$ such that: $a_1x_1 + a_2x_2 + .... + a_nx_n \le b$ Is there an obvious solution? I had originally thought this was a simple matter of choosing the largest…
mips
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Express the constraint "$x = 0$ or $y = 0$" in linear programming

How to express the constraint "$x = 0$ or $y = 0$" in a linear program? Is it possible at all?
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What if we get fractional value while finding the numbers of workers in a linear programming problem?

I came across a LP problem in which a factory recruited workers on daily basis giving them wages per day. I don't remember the figures but I remember what was in the question. We had to find the number of male and female workers which should be…
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How to find what maximizes the total net profit?

A meat packing plant produces $480$ hams, $400$ pork bellies and $230$ picnic hams every day; each of these products can be either fresh or smoked. The total number of hams, bellies and picnics that can be smoked during a normal working day is…
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What is the definition for "equivalent linear programming problems"?

My question is in the title: How can we define exactly when two linear programming problems are equivalent? I used to see some definition such as "$B$ is equivalent to $A$ if $B$ is solvable, then $A$ is solvable", but it is quite confusing to…
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Transforming an array of equations as a canonical form?

Today was my first course of linear programing, I've just read again my notes and I'm not sure how does this array of equations actually transformed itself. \begin{equation*} \begin{cases} \max a^Tx+b^Ty+c^Tz \\ \\ Ax + By+ Cz…
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Problem in forming linear equations in Linear Programming problem

Here is the given question: A toy manufacturer produces two types of dolls; a basic version doll $A$ and a deluxe version doll $B$. Each doll of type $B$ takes twice as long to produce as one doll of type $A$. The company have time to make a maximum…
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Linear programming problem using the simplex algorithm, dual problem...

I want to maximize $z = 12x + 20y$ with the following constraints: $$\eqalign{ & 2x + 8y \le 180 \cr & 4x + 4y \le 120 \cr & x,y \ge 0 \cr} $$ I need the simplex tableau to find optimal solution but also I need to determine the dual…
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LP Constraint Problem

If you have an investment fund which has four options $x_1,x_2,x_3,x_4$ More should be invested in the combination of funds $x_2$ and $x_3$ than funds $x_1$ and $x_4$ by a ratio of at least $1.5:1$. The constraint I have formed is as…
Phil
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