It depends on what format you are using for the cell, and if you use format
General the number of digits displayed can depend on the width of the cell
and the size of font. I expect that if you reformat your
original -0.55, -1.0 , 1.65 to show 14 decimal places, you'll see that they
are not exactly as you were seeing them.
--
David Biddulph

"Marcus" wrote in message
...
I have a problem and need your advise asap.
When I try to sum up a few cells that contain decimal number, it turn out
to
be a long sequence of number. Please used only the following example to
test
on the excel 2000
e.g. -0.55, -1.0 , 1.65 , then sum up the cell using formula like
=sum(S1;S3).
it appear as 0.1 but when you copy and paste special this total sum to
another cell,
it appear as 0.099999999999.
Why will such things happen? Is it the excel error? Pls advise.