Here's an example of rounding errors:

I have in the formula =LN(RAND()^2) in C2:E5 and then I sum C2:C5, D2:D5,
and E5 and then do your formulas in A1 and B1. So far, everything is as you
create it.

Then I widened the cells so that 15 digits are displayed.

Finally, in A4 I put the formula =IF(A1=B1,"",1) so that a 1 shows if the
two cells are not exactly equal. Pressing F9 repeatedly yields a 1
eventually (and my guess is that the occurrence of 1s could be predicted if
one were so inclined.) In any event, the following two values triggered the
1:

0.0102071029117790000

and

0.0102071029117798000

As you can see these are not equal but only very approximately equal, due to
Excel's 15 digit of precision calculation limit.

Dave

--
A hint to posters: Specific, detailed questions are more likely to be
answered than questions that provide no detail about your problem.


"danieldc" wrote:

Hi, I just found this "feature" at Excel formulas today.

Please, have a look at: http://danielgudang.multiply.com/journal/item/192
(in portuguese, but images show all)


Let me explain:


some cell C1 = sum (C2:C5)
some cell D1 = sum (D2:D5)
some cell E1 = sum (E2:E5)


A1 = C1 - D1 - E1
B1 = C1 - (D1 + E1)


A1 = B1 ??? Oh, not always!


Sometimes A1 will be +0, sometimes -0.


Really strange!