This so-called error is the result of the computer converting decimals
numbers (base 10) to binary (base 2)
See one or more of these
IEEE 754
Floating-point arithmetic may give inaccurate results in Excel
http://support.microsoft.com/kb/78113/en-us
(Complete) Tutorial to Understand IEEE Floating-Point Errors
http://support.microsoft.com/kb/42980
What Every Computer Scientist Should Know About Floating Point
http://docs.sun.com/source/806-3568/ncg_goldberg.html
http://www.cpearson.com/excel/rounding.htm
Visual Basic and Arithmetic Precision
http://support.microsoft.com/default...NoWebContent=1

--
Bernard V Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme
remove caps from email

"Captain" wrote in message
...
Your problem is exactly the same as mine. I found that there was an error
in
the 13th decimal place when subtracting exactly $1,015.00 from $1,183.30!
Get around this error by writing a formula that accepts a calculation as
correct if it matches the expected answer to within $.01 or within .01%,
etc.
example: IF(AND(A1<B1+.01,A1B1-.01),"OK","error").
--
E. Polizzi


"BobD" wrote:

I am using Excel 2003 Professional Edition. If you include the following
formula into a cell, it produces a result of 8.74999999999999 if you
expand
the decimal places to 16. The correct answer is 8.75. The formula is
((17.15-17)*10/6+17)-((8.3-8)*10/6+8). This only happens if you use 17.15
and
8.3. I came across this when using a process to convert times to
decimals
and then subtract one from the other. Anyone have any ideas?
--
BobD