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Re: Formula Wanted



>> to do my own on a spread sheet, and would like the formula.

>> I don't know of any way to do an iterative solution to this problem
>> in a spreadsheet, but then again I don't know much about spreadsheets.

In Lotus 123, the function is called Goal Seeker, and in Excel, Solver. 
Having used both, I like the Excel function much better, with this
caveat:  make some option settings to limit the iterations so your
computer doesn't "go to lunch" while you wait for an answer.

Play with these settings in options to fine tune your process:

Iterations

Limits the time taken by the solution process by limiting the number of
interim calculations. While you can enter a value as high as 32,767, the
default value of 100 is adequate for most small problems.

Precision

Controls the precision of solutions by using the number you enter to
determine whether the value of a constraint cell meets a target or
satisfies a lower or upper bound. Precision must be indicated by a
fractional number between 0 (zero) and 1. Higher precision is indicated
when the number you enter has more decimal places ¾ for example, 0.0001
is higher precision than 0.01. The higher the precision, the more time
it takes to reach a solution.

Tolerance

The percentage by which the target cell of a solution satisfying the
integer constraints can differ from the true optimal value and still be
considered acceptable. This option applies only to problems with integer
constraints. A higher tolerance tends to speed up the solution process.

I have a pair of the old HP Palmtop computers (HP95LX, HP100LX)  They
both have Lotus built into ROM, and BOTH have a builtin fcalculation
which includes a very nice solver function.  Wanna buy an old plamtop?

73 and I hope this helps a little

Mike Gilchrist kf4fdj@amsat.org
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