Incorrect Slack Value Returned in Solver Answer Report

This article was previously published under Q116390
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In Microsoft Excel, when you use the Solver add-in to find a solution, andyou add a constraint that consists of one cell value that depends onanother cell value, the Slack value that appears in the Constraint table onthe Answer report for that cell is incorrect.
The slack value that appears on the Answer report when you use theSolver add-in is the absolute value of the difference between the twoparts of a constraint. The left part of the constraint is theconstraint cell, while the right part of the constraint is the targetvalue for the constraint cell. When the right part of the constraintis a constant, the reported Slack value is correct. However, when theright part of the constraint can vary during the solving, the Slackvalue is not calculated using the final value of the right part ofthe constraint.

The following is an example of a constraint where the second part ofthe constraint is a constant:
   $A$1 <= 10				
The following is an example of a constraint where the second part ofthe constraint varies during the solving:
   $A$1 <= $A$2				
Using the constraint above, if the final value of the constraint cell($A$1) is 5, and the final value of the target cell ($A$2) is 10, theSlack value for the constraint cell A1 should be 5. However, when youuse Solver with a constraint such as this second example, the Slackvalue for cell $A$1 is incorrect on the Answer report.
Microsoft has confirmed this to be a problem in the Microsoftproducts listed at the beginning of this article. We are researchingthis problem and will post new information here in the MicrosoftKnowledge Base as it becomes available.
For more information about Creating A Report Using Solver, choose theSearch button in Help and type:
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Article ID: 116390 - Last Review: 09/13/2013 18:49:26 - Revision: 1.1

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