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I found an Excel calculation error using Sum. When some of the numbers are removed, the error disappears, although there is only zero's behind the 3rd digit after the decimal place. Answer of sum in last row.

28.04000000000000000000000000

26.86000000000000000000000000

26.92000000000000000000000000

27.02000000000000000000000000

27.34000000000000000000000000

29.80000000000000000000000000

27.10000000000000000000000000

26.82000000000000000000000000

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27.12000000000000000000000000

27.30000000000000000000000000

27.44000000000000000000000000

27.54000000000000000000000000

27.48000000000000000000000000

27.44000000000000000000000000

26.88000000000000000000000000

27.72000000000000000000000000

26.66000000000000000000000000

26.92000000000000000000000000

29.40000000000000000000000000

26.90000000000000000000000000

26.92000000000000000000000000

27.60000000000000000000000000

26.88000000000000000000000000

27.04000000000000000000000000

27.40000000000000000000000000

27.24000000000000000000000000

26.96000000000000000000000000

27.10000000000000000000000000

26.98000000000000000000000000

27.08000000000000000000000000

27.44000000000000000000000000

27.06000000000000000000000000

27.10000000000000000000000000

27.18000000000000000000000000

26.24000000000000000000000000

26.88000000000000000000000000

27.16000000000000000000000000

27.66000000000000000000000000

27.28000000000000000000000000

26.78000000000000000000000000

26.82000000000000000000000000

11.36000000000000000000000000

27.10000000000000000000000000

26.80000000000000000000000000

28.00000000000000000000000000

29.88000000000000000000000000

26.74000000000000000000000000

26.86000000000000000000000000

26.80000000000000000000000000

26.88000000000000000000000000

27.22000000000000000000000000

26.96000000000000000000000000

26.94000000000000000000000000

26.26000000000000000000000000

25.52000000000000000000000000

34.26000000000000000000000000

33.30000000000000000000000000

32.84000000000000000000000000

28.26000000000000000000000000

26.46000000000000000000000000

26.72000000000000000000000000

27.20000000000000000000000000

28.26000000000000000000000000

26.96000000000000000000000000

12.90000000000000000000000000

26.92000000000000000000000000

26.86000000000000000000000000

22.94000000000000000000000000

29.50000000000000000000000000

27.38000000000000000000000000

26.86000000000000000000000000

27.32000000000000000000000000

26.92000000000000000000000000

26.80000000000000000000000000

35.26000000000000000000000000

29.74000000000000000000000000

27.92000000000000000000000000

26.94000000000000000000000000

27.14000000000000000000000000

27.06000000000000000000000000

26.96000000000000000000000000

27.30000000000000000000000000

29.40000000000000000000000000

29.14000000000000000000000000

29.92000000000000000000000000

27.14000000000000000000000000

26.64000000000000000000000000

27.30000000000000000000000000

27.26000000000000000000000000

28.58000000000000000000000000

27.30000000000000000000000000

35.06000000000000000000000000

30.36000000000000000000000000

27.40000000000000000000000000

27.02000000000000000000000000

27.46000000000000000000000000

27.30000000000000000000000000

27.28000000000000000000000000

27.24000000000000000000000000

32.32000000000000000000000000

30.08000000000000000000000000

27.46000000000000000000000000

27.22000000000000000000000000

34.14000000000000000000000000

26.92000000000000000000000000

30.22000000000000000000000000

28.16000000000000000000000000

27.08000000000000000000000000

35.00000000000000000000000000

26.94000000000000000000000000

27.34000000000000000000000000

27.90000000000000000000000000

26.94000000000000000000000000

28.12000000000000000000000000

26.78000000000000000000000000

27.00000000000000000000000000

26.88000000000000000000000000

27.06000000000000000000000000

28.16000000000000000000000000

29.80000000000000000000000000

34.90000000000000000000000000

26.44000000000000000000000000

27.66000000000000000000000000

26.96000000000000000000000000

29.98000000000000000000000000

27.34000000000000000000000000

30.10000000000000000000000000

35.10000000000000000000000000

27.12000000000000000000000000

27.14000000000000000000000000

24.16000000000000000000000000

27.26000000000000000000000000

28.28000000000000000000000000

30.40000000000000000000000000

27.16000000000000000000000000

26.68000000000000000000000000

35.28000000000000000000000000

23.08000000000000000000000000

26.86000000000000000000000000

27.02000000000000000000000000

30.02000000000000000000000000

32.74000000000000000000000000

33.24000000000000000000000000

34.02000000000000000000000000

35.06000000000000000000000000

28.14000000000000000000000000

27.10000000000000000000000000

30.36000000000000000000000000

30.04000000000000000000000000

27.32000000000000000000000000

23.30000000000000000000000000

28.16000000000000000000000000

30.04000000000000000000000000

26.64000000000000000000000000

27.04000000000000000000000000

27.90000000000000000000000000

35.06000000000000000000000000

27.10000000000000000000000000

26.76000000000000000000000000

27.04000000000000000000000000

27.06000000000000000000000000

27.70000000000000000000000000

30.24000000000000000000000000

34.60000000000000000000000000

24.00000000000000000000000000

36.72000000000000000000000000

21.88000000000000000000000000

27.08000000000000000000000000

27.26000000000000000000000000

30.22000000000000000000000000

26.98000000000000000000000000

28.04000000000000000000000000

35.32000000000000000000000000

27.24000000000000000000000000

26.68000000000000000000000000

22.26000000000000000000000000

22.28000000000000000000000000

24.12000000000000000000000000

27.18000000000000000000000000

28.14000000000000000000000000

35.08000000000000000000000000

29.98000000000000000000000000

33.98000000000000000000000000

36.62000000000000000000000000

26.90000000000000000000000000

27.44000000000000000000000000

27.14000000000000000000000000

26.98000000000000000000000000

29.92000000000000000000000000

27.02000000000000000000000000

30.10000000000000000000000000

35.24000000000000000000000000

26.90000000000000000000000000

27.10000000000000000000000000

27.16000000000000000000000000

26.60000000000000000000000000

29.96000000000000000000000000

26.88000000000000000000000000

27.98000000000000000000000000

27.34000000000000000000000000

32.68000000000000000000000000

35.04000000000000000000000000

26.96000000000000000000000000

29.92000000000000000000000000

13.68000000000000000000000000

13.48000000000000000000000000

27.10000000000000000000000000

33.94000000000000000000000000

26.64000000000000000000000000

29.80000000000000000000000000

29.96000000000000000000000000

26.70000000000000000000000000

26.80000000000000000000000000

26.60000000000000000000000000

26.96000000000000000000000000

34.56000000000000000000000000

26.92000000000000000000000000

27.02000000000000000000000000

33.06000000000000000000000000

26.80000000000000000000000000

27.70000000000000000000000000

27.56000000000000000000000000

28.46200000000000000000000000

27.34000000000000000000000000

27.10000000000000000000000000

34.68000000000000000000000000

25.54000000000000000000000000

27.22000000000000000000000000

27.34000000000000000000000000

34.92000000000000000000000000

27.52000000000000000000000000

29.88000000000000000000000000

27.50000000000000000000000000

27.26000000000000000000000000

27.92000000000000000000000000

34.54000000000000000000000000

27.22000000000000000000000000

27.34000000000000000000000000

30.12000000000000000000000000

29.98000000000000000000000000

28.14000000000000000000000000

27.26000000000000000000000000

27.34000000000000000000000000

27.32000000000000000000000000

26.98000000000000000000000000

30.30000000000000000000000000

34.84000000000000000000000000

28.22000000000000000000000000

21.70000000000000000000000000

28.72000000000000000000000000

28.00000000000000000000000000

27.04000000000000000000000000

27.90000000000000000000000000

28.14000000000000000000000000

27.78000000000000000000000000

-----------------------------

7159.882000000010000000

=============================

I read on the Internet that Excel is supposed to be accurate up to 15 digits after the decimal place so above could be a bug?

Aibin Drug
2011-06-18 22:05:00
First select boxes with wrong numbers then right click and go to Format Cells. Then in Number menu go to the “Number” (which is under “General”) change decimal palces to 2 (or whatever you want).
Aibek
2011-06-19 07:01:00
thank for the input :)
Bruce Epper
2011-06-16 07:58:00
Numbers are stored in a computer in the binary number system.  Conversion from base 10 to base 16, base 8, or base 2 will almost always introduce error since the computer is using a fixed amount of memory to store this new representation of the data.  This error becomes magnified when performing other operations on the data, hence the discrepancy you see in your result of the addition of these 255 values.  In this case, it appears that once you cross the 229 element line, the error becomes apparent.  This is one of the reasons why you should not display more decimal places than necessary for the data you are representing, i.e., if your initial data only used 3 decimal places, only display 3 decimal places for your results (as well as your input data).  You will not be increasing precision by displaying more decimal places in the result and you can end up confusing your audience when they see errors introduced by base conversion and rounding.
dfdf
2012-05-25 12:21:52
- 754,462,783,982,350,000 754,462,783,982,349,000 if you remove 2 zero's - they sum correctly - and interestingly this is when they are 16 chars long..if you add zero's the sum is even odder!thanks you've explained my bug..
Aibin Drug
2011-06-15 00:04:46
First select boxes with wrong numbers then right click and go to Format Cells. Then in Number menu go to the "Number" (which is under "General") change decimal palces to 2 (or whatever you want).