excel adding values incorrectly

A simple formule to add two cell values is calculating an incorrect value..
a chemical engineering spreadsheet with cells formatted in "accounting" to 12 decimal places..

Excel is "adding" 100 units at about the 10th decimal place see example below..

Cell A1= 55,221.60000000000
Cell A2= 968.80000000000

Formula reads " =a1+a2
Result = " 56,190.400000000100
why is the 10th decimal a "one" ???????

using Office 200

I don't know but it's always done this e.g. £10.00 minus £9.80 will give 0.199999999999999 when you get to 14 decimal places! Only way I have found to overcome it is to use the TEXT functio

Hope this help

Sheil

I have read about this "error". It has to do with the significant figures
and the hexadecimal calculations used internally. Do a search on
"hexadecimal" in this or other excel groups and you will find detailed
explanations and ways to circumvent the problem.


"Jazz" <anonymous@discussions.microsoft.com> wrote in message
news:C1CBEAD8-7606-4F7B-946D-6AA2F52694ED@microsoft.com...
> A simple formule to add two cell values is calculating an incorrect
value...
> a chemical engineering spreadsheet with cells formatted in "accounting" to
12 decimal places...
>
> Excel is "adding" 100 units at about the 10th decimal place see example
below...
>
> Cell A1= 55,221.600000000000
> Cell A2= 968.800000000000
>
> Formula reads " =a1+a2"
> Result = " 56,190.400000000100"
> why is the 10th decimal a "one" ????????
>
> using Office 2002
>