Solver's Linearity Condition Error Message Returned

SUMMARY

The following error message may be returned when the model is known to be linear:

   The linearity condition is not satisfied. Turn off the Assume
   Linear Model check box and then run Solver again

MORE INFORMATION

This happens when your initial guess for the solution is significantly different from the optimal solution and the Assume Linear Model check box is checked. This error message can be ignored in most cases because Solver has reached a suitable solution that is very close to the one that would be reached with the Assume Linear Model check box unchecked.

Steps to Reproduce Problem

1. Create a spreadsheet with the following data:

       A1: 10000     B1: 1.50        C1: =A1*B1
       A2: 10000     B2: 1.75        C2: =A2*B2
                                     C3: =SUM(C1:C2)
   
   

2. From the Formula menu, choose Solver.

3. Enter $C$3 in the Set Cell text box.

4. Select Min.

5. Enter $A$1:$A$2 in the By Changing Cells text box.

6. Choose the Add button.

7. Enter $A$1:$A$2 in the Cell Reference text box.

8. Click the Down Arrow button and select >=.

9. Enter 0 in the Constraint text box. Choose OK.

10. Choose the Options button.

11. Check the Assume Linear Model check box. Choose OK.

12. Choose the Solve button.

   The linearity condition is not satisfied. Turn off the Assume
   Linear Model check box and then run Solver again

Workarounds

1. Choose OK to keep the current solution. It may be accurate.

2. Turn off the Assume Linear Model check box and then run Solver again.

3. Set the variable cells ($A$1 and $A$2 in the above example) equal to 1 or some smaller value and then run Solver again.

REFERENCES

"Microsoft Excel Solver User's Guide." Version 3.0, pages 11-20.