# How to "Solve" Solver Optimization Mix Problem Errors

1. ## How to "Solve" Solver Optimization Mix Problem Errors

Hello all,

I'm a little new to solver, so i'm probably missing something very simple, but here's my problem.

I have a list of technologies with associated capabilities (score of 1-5). I have a set of requirements for said capabilities (score of 1-5). I have costs associated with each technology.

I would like to run solver to find the most optimal combination of capabilities such to maximize the total score, given a cost constraint.

However, when I run Solver in the attached, I keep getting either a linearity error or a "solver cant find solution". I know there's at least a feasible solution (I've done it myself).

Best,
Chris

2. ## Re: How to "Solve" Solver Optimization Mix Problem Errors

Try this:

D24 =SUMIF(Table1[Selected? 0 or 1],1,Table1[Cost])

Then run the solver.

I get B7 = 6.9166

3. ## Re: How to "Solve" Solver Optimization Mix Problem Errors

Hi falcondude,

Thanks for the quick reply. I tried your suggestion and got 2.6, Then I changed the constraint to 43k and got a linearity error. See attached.

4. ## Re: How to "Solve" Solver Optimization Mix Problem Errors

Hmm. I'm not sure why you would have gotten 2.6.

I did have to recreate the formulas in D26:M26 using MAX and IF since I don't have the MAXIFS function.

See attached.

As far as the linearity error is concerned, I am getting that on my end as well when I lower the constraint to anything less than 318,473.

I'm not too familiar with the different types of solving methods. I'll see if someone knows more about them.

5. ## Re: How to "Solve" Solver Optimization Mix Problem Errors

It seems to work when I change the solving method to Evolutionary but it takes a couple of minutes.

6. ## Re: How to "Solve" Solver Optimization Mix Problem Errors

That's interesting - works for me as well.

I'll have to do a bit of reading to see what the difference is. Thank you for taking the time to help out!

7. ## Re: How to "Solve" Solver Optimization Mix Problem Errors

You're welcome. Happy to help.

If that takes care of your original question, please select Thread Tools from the menu link above and mark this thread as SOLVED.

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