GRG solver cannot set up nonlinear problem

[shaoshao]

Problem 2: I need to find the barrels of oil to extract in Year 1 and 2 in order to maximise profit. The formula of sales and cost are given as well as the constraints. The cost is nonlinear. This is a really simple model but excel wouldn't even set up the GRG. Can someone please let me know what the error is?

Problem 3: I need to find the advertising expenses in order to maximise the average market share in 12 months. The customer inflow is nonlinear. Again, I ran GRG and the error message "Invalid property" showed up. Can someone please help fix the model?

I have made so many attempts and I don't know what's wrong. I am really desperate at this point. Please kindly help, internet.

[RiskTrainer]

Try replacing profit with cell reference $D$8 in your objective function and then run solver. Also make sure that you have clicked the non-negative value option so that your barrels don't turn negative. There may be an issue with your range reference. I made the change and the model ran.

[Hydraulics]

In the first model, I guess the sales formula in B6 should be

=80*B5

rather than 80-B5. Morever, as RiskTrainer wrote, your objective cell should be D8.

With this setup, and adding an int condition on the number of barrels (not really required), the maximum profit is 914.


The error message in the second model comes from the option "Require Bounds on Variables" that has been set in the dialog for the Evolutionary Engine.
Even if you later change your mind and switch back to GRG or Simplex, Solver will remember it and warn you that you have not defined upper and lower boundaries for all your variables.
Just uncheck it and the model will run fine (even though I don't know if the result makes sense).

HTH,

Francesco

[shaoshao]

Thanks for the advise!!!!

[shaoshao]

THANK YOU SO MUCH for the big help!!! You saved my life!!!!!