## Introduction: How to Use the Solver Tool in Microsoft Excel

The purpose of this guide is to introduce people to the computer program Microsoft Excel. We will specifically be focusing on the solver tool aspect of the program and how users can use it to their advantage. This guide will cover all parts of the solver tool function and a step-by-step guide on how to use it. In Microsoft Excel, Solver is part of a category of commands called what-if analysis tools. The Solver is an add-in for Microsoft Excel which is used for the optimization and simulation of business and engineering models. It solves complex linear and non linear problems. With Solver, you can find an optimal (maximum or minimum) value for a formula in one cell. This is called the objective cell, which is subject to constraints, or limits, on the values of other formula cells on a worksheet. Solver works with a group of cells also called decision variable cells, that participate in figuring out the formulas in the objective and constraint cells. Solver adjusts the values in the decision variable cells to satisfy the limits on constraint cells and produce the result you want for the objective cell. Now lets open up Excel and get started!

## Step 1: How to Download & Enable Solver Add-in in Excel.

The solver add-in is included by default in Microsoft Excel but is disabled until the user enables it for use. There are a few easy steps required to enable solver. To enable it, you fist need to click on the file menu and then go to the options tab. Next, the excel options box will come up, click on the solver add-in located under the add-ins heading and make sure it is highlighted in blue. Now, click the go box, which is located in the manage excel add-ins at the bottom of the excel options screen. After you have clicked go the add-ins box will come up. In the add-ins box check the box next to solver add-in, which is located under the add-ins available heading, and then click the okay button. Now that solver has been enabled you will need to know how to locate it for use. Open up excel and go to the data tab and click it, and all the way to the right solver is located under analysis.

## Step 2: Example Function

Excel Solver is used by engineers and mathematicians to solve a large variety of mathematical equations and systems. Solver is equipped with functions that allow users to find the root/solution of an equation. A simple function is given below as an example problem where someone would wish to find the root of the function. The function is: y = 2x^2 + 3x – 4. Solver will solve the equation for 0, i.e. 2x^2 + 3x -4 = 0, as anyone would normally do by hand. In the following illustration, the first step of all excel solutions is to properly define the function that is being solved. The second step is to assign the variable of the function to one specific cell. Assign the variable x to the cell B1 by typing x= in cell A1 and typing nothing in cell B1. Define the function in cell B2 by typing f(x)= in cell A2 and typing =2*B1^2+3*B1-4 in cell B2. Cell B1 plays the part of x in the formula, and by changing the values in cell B1, you will notice that the results of the function will change. The goal is to have cell B1 vary the value of x until the cell B2 (the function) is 0.

## Step 3: Understanding the Solver Parameters Box

Once you click the Solver option, the Solver Parameters dialogue box will appear. Once here, you will need to specify the parameters in order to run the solver. These parameters will vary depending upon your problem. The Set Target Cell box should contain the cell location of the objective function for the problem under consideration. Max or min may be selected for finding the maximum or minimum of the set target cell. If value is selected, the Solver will attempt to find a value of the target Cell equal to whatever value is placed in the box just to the right of this selection. The Cells box should contain the location of the decision variables for the problem. Finally, the constraints must be specified in the Subject to the Constraints box by clicking on Add. Change allows you to modify a constraint already entered and delete allows you to delete a previously entered constraint. Reset all clears the current problem and resets all parameters to their default values. Options brings up the Solver options dialogue box. The guess selection is not particularly useful for our purposes and will not be discussed here.

## Step 4: Setting the Target Cell and Equal To

With Solver, you can find an optimal values or solutions for a formula in one cell. This cell is called the target cell. The target cell will represent the objective or goal. If a scenario in which the production manager of a firm would presumably want to maximize the profitability of the Product during each month, the target cell would be used. Now, back to the example function problem given in step 2: y = 2x^2 + 3x – 4.

Set Target Cell: Solver is asking you to identify the position of the function you wish to solve. In this example the function was placed in the cell B2. After step 2 has been completed go to solver and click on it. The solver parameters dialogue box will pop up. To set the target cell you must use the proper symbols that excel understands, you cannot type in B2. To set the target cell correctly you must type in $B$2.

Set Equal To: The equal to option allows you to identify the operation you wish to carry out with your chosen function. The options that equal to gives are max, min, value. Max would be if you were looking for the maximum value of a function, and min would be used to find the minimum value of a function. The Value option if for you to select the value you want the equation to be solved for. In the given example from step 2, the function is meant to take on the value of 0. Go to equal to, then select value of: and type 0 in the box next to it.

## Step 5: Setting the Changing Cells and Solving

Set By Changing Cells: Changing cells can also be called variable cells, because their main purpose is to identify the cells that contain the variables of the function. In the given example from step 2, B1 is the cell containing the value of the variable x. Go to the box under by changing cells and type in $B$1, do not forget the $ symbols or excel will not understand. Finally, click solve at the bottom of the solve parameters dialogue box and click solve. Solver will now perform the operation you asked it to and will give you the solution x=0,850781. The solution will appear in cell B1.

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