Tricky(?) simultaneous equations in VBA

[Mr. Numbers]

Hi!

I have successfully written a macro to solve a set of simultaneous equations, as follows:

a + b + c = 24
a - b = 2
b - c = 2


My macro is fine:

Dim ValInv As Variant
Dim EqResults As Variant
Dim EqVal(1 To 3, 1 To 3) As Double
Dim EqGive(1 To 3, 1 To 3) As Double

EqVal(1, 1) = 1
EqVal(1, 2) = 1
EqVal(1, 3) = 1
EqGive(1, 1) = 24

EqVal(2, 1) = 1
EqVal(2, 2) = -1
EqVal(2, 3) = 0
EqGive(2, 1) = 2

EqVal(3, 1) = 0
EqVal(3, 2) = 1
EqVal(3, 3) = -1
EqGive(3, 1) = 2

Set WF = WorksheetFunction
ValInv = WF.MInverse(EqVal)
EqResults = WF.MMult(ValInv, EqGive)

Cells(1, 1) = EqResults(1, 1) 'This is a
Cells(2, 1) = EqResults(2, 1) 'This is b
Cells(3, 1) = EqResults(3, 1) 'This is c


I get a=10, b=8, c=6

"So what's the problem?" I here you ask. Well, suppose one of the calculations were multiplication, as shown below:

a + b + c = 22
a - b = 10
b * c = 16

The answer should be: a=12, b=2, c=8

However, I have NO idea how to accomplish this. Or am I just being so stupid and the answer is obvious? Running the matrices doesn't seem to be the answer.

Thanks for anyone who takes their precious time to read my query.

 

[wigi]

Hello

Could you use the Excel Solver?

 

[Mr. Numbers]

Hello Wigi

First, I'm sorry if my title was a little vague - this is the first time I've ever put a question on a forum (I've been trying so hard to make a huge macro myself over the last 2 years, using books or other net info), and I'm no professional.

I'll look into Excel Solver. I had noticed it before, but thought it was something which could only be accessed 'manually' (i.e. entering data into a window) and not called like a function from within a macro.

Give me a week to try to make something.

I REALLY appreciate your post.