We will add several constraints for our rules:ġ. Hint: You can try the Guess button next to the Range Reference and Solver will take a Guess at what cells the problem is dependent on.Īlways check this if you use it, especially in complex models.Ĭonstraints are the rules which define the limits of the possible solutions to the problem
We want to let Solver change the number of items in each bucket, this is the range: $C$2:$D$9 By Changing Cells:Ĭhanging Cells: refers to the cells which will be modified by Solver to try and solve the problem. This allows us to use Min as an Equal To: Valueīut for now we can just leave G11 as =G10-H10 and we will set the Equal To: section as 0. A minimal value will be achieved when all the Items are placed in Bucket A, as our equation for G11 will then have 0 – Total which is –Total, which is more minimal than 0.Īnother way to constrain this is to Change G11 to =Abs(G10-H10) It might sound strange but we don’t want to minimise that difference. We want to achieve the same value in each Bucket and so the difference between the Buckets will be 0. The Equal To: section defines what we want to do with our Target Cell. Our Target cell is G11, The difference between the 2 Buckets values Equal To: This is the Target cell which is the cell which you are trying to solve the problem for. This section will explain the solver window and its use in defining the problem within solver. We will discuss how these constraints are used in the next section The Solver Window We also know that the Total Number of Items is 8, this is another constraint.
Secondly the Buckets Values must be Integers We also know that an item can only be in Bucket A or Bucket B, it can’t be in both and can’t be Broken apart.įirstly The Total column must be equal to 1 We want to have G11 as low as possible but greater than or equal to 0. The difference between the 2 buckets in our example is cell G11, the sum of Bucket 2 values minus the Sum of Bucket 1 values. Our main requirement is to minimise the difference between the value of the 2 buckets. These requirements, rules and constraints guide solver and set limits which allow solver to quickly narrow in on the answer.
How to solver in excel series#
To apply solver we need to define a series of requirements, rules and constraints. The problem is that there are 2 8 or 256 combinations of answers, and to test them all manually at 1 every 5 seconds would take 21.3 minutes, assuming we can keep up that pace and remember which was the best combination. I have applied some conditional formatting to show when a cell has a value > 0. Now we can place values of 1 in the buckets manually and Excel will show us the value of each Bucket and the Difference between them in Cell G11. Mdsuhair’s original problem was to minimise the difference between the sum of the values in the 2 buckets. We do this by multiplying the Items Value by the Buckets (In/Out) valueįinally we need to add up the values in each Bucket and work out the difference between them We also know that we need to work out the Value of each Item in each Bucket We can start by adding a Total Column, which counts items in Buckets A + Bucket B for each Item, It then totals the totals. We will put values of 1 into a Bucket for each Item to show that it is assigned to that Bucket and a value of 0 to show that the bucket is empty (In/Out) Value. To do this we need to assign each item into a Bucket. He wants to know which items should be combined so that the sum of the values of the items is nearly equal. Mdsuhair had a series of 8 Items each which had a value: This post is based around a worked example Solver Example File, the file is compatible with all versions of Excel. Solver will now appear as a New Tab on the Data, Analysis Tab Solver is an Excel add-in supplied with Excel, but not enabled by default.įile, Excel Options, Add-ins, Manage Excel Add-ins, Select the Solver Add-in checkbox It solves the problem by adjusting a number of input cells according to a set of criteria or constraints which are defined by the user. This goal may be to minimse, maximise, or achieve some target value. Solver is an Excel add-in that can solve problems by enabling a Target cell to achieve some goal. Users should note that the screen shots may not match your version although the functionality will, some of the functions appear in different locations in different versions of Solver. It uses Solver and screen shots from Excel 2007.Īll versions of Excel have solver available. This post will walk us through the solution to the problem using Solver. What formula can I use to divide a group of numbers into 2 groups so that the Sum of each of the 2 groups is as equal as possible?
In April 2011, Mdsuhair asked a question at the Forums
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