On Fri, 8 Jul 2005 15:24:05 -0500, ddelong
wrote:


Yes I had a typo in my sum, it should've been sum(c10:C13) good catch
!

Thank you for the explanation but it still doesn't explain why I could
use other numbers to add up to 28853.09 and be fine or even simply type
28853.09 in that field and not use the sum function.

Should I use the round function EVERY time I use the sum function so
that this can't happen ?

If someone could elaborate I would appreciate it.

Jerry W Lewis writes about this frequently. And yes, if you are interested
that two separate SUMS equate exactly to zero, you will either have to use the
ROUND function, or use INTEGER math.

Here is one of Jerry's previous postings about a similar issue. The concept is
applicable to your problem:

===========================
the easiest way to think about these issues is to recognize that
Excel's documented limit of 15 decimal digit accuracy relates to the
accuracy of decimal/binary conversion. Thus your problem can be thought
of as
-30584.0100000000?????
30585.6000000000?????
----------------------
1.5900000000?????
which is consistent with your result of
1.59000000000015

The binary approximation to 30584.01 is 8406868654754365/274877906944
The binary approximation to 30585.6 is 4203652855313203/137438953472
The exact difference between these numbers is 437055872041/274877906944
which in decimal is 1.59000000000014551915228366851806640625, or
1.59000000000015 to 15 figures.

In keeping with Excel's documented limit of 15 decimal digit accuracy,
if you ask for more than 15 decimal digits, the trailing digits are
arbitrarily displayed as zero.

Jerry
===================================
--ron