Guys,

Something has gone screwy here!

Divide by 11 is correct.

The total = net * (1 + tax%/100)
thus
net=total/(1 + tax%/100)

But - be warned, you simply cannot do sales tax this way.  Each country
as strict laws which set the amount of decimal places the calculation
has to be correct to (in the UK is it 7).  Then there is another set of
rules has to how to round a fractional result, in the UK that is halve
even if memory serves.

So your steps are this:
1) Make sure everything is in double precision - or use a big decimal class
2) Make sure you know the rounding rules
3) Make the calculation in three steps

Kind of like this - but must be tailored to your local laws

const oneHundred as double = 100.0
const one as double = 1.0
const rounder as double = 7.0
function GetTaxFromGross(taxPercent as double, gross as double)
    dim tmpd as double
    dim tmpl as long
    tmpd=gross/(one + taxPercent/oneHundred )
    tmpl=clng(tmpd * (rounder + one))
    ' Better check this - done from memory!
    if tmpl mod 20 > 10 then
        if tmpl mod 10 > 5 then
            tmpl=tmpl + 10 -(tmpl mod 10)
        else
            tmpl=tmpl  -(tmpl mod 10)
        end if
    else
        if tmpl mod 10 > 5 then
            tmpl=tmpl  -(tmpl mod 10)
        else
            tmpl=tmpl + 10 -(tmpl mod 10)
        end if
    end if
    return tmpl/rounder
end function

Please pleas please - note this code is a raw translation of the Java
version I wrote a couple of years ago - it is a guideline only - you
must spin your own!

Best wishes

AJ

www.deployview.com
www.nerds-central.com
www.project-network.com