# Thread: (9,8 - 9,1) - 0,7 = 0,000000000000001110223024625160 ??

1. ## (9,8 - 9,1) - 0,7 = 0,000000000000001110223024625160 ??

Dear All,

Writing from Europe, therefor I use decimal commas instead of decimal points but that should not be the problem. W7x64, Excel 2003.

I was checking some scanned numbers to see if they were correct. Then I did some auto-formatting (if scanned value is not equal to what excel calculates, go red) and sure enough I found some minor errors in the data.

But what puzzled me most was that 9,8 - 9,1 did not match 0,7.

A1=9,8 B1=9,1 C1=0,7 D1=(A1-B1) E1=(D1-C1) Now E1 shows: 1,11022E-15 which equals 0,000000000000001110223024625160

Expanding the decimal positions of D1 it will go all the way to 0,70000000000000100000000000000000000

This puzzles me even more, because I think that 0,70000000000000100000000000000000000 - 0,7 does not match 1,11022E-15

I did repeat this starting from scratch typing just the above fields. :-(

/\
\7erard

2. Hi,
It's a floating point precision problem. Have a read of Chip's page here: http://www.cpearson.com/Excel/rounding.htm

3. ## The Following User Says Thank You to rory For This Useful Post:

Sr.Gerard (2012-06-13)

4. Hi rory,

A floating point precision problem is what you call it? I never suspected that 9,8 - 9,1 could provoke rounding errors. ;-)

Thanks.

/\
\7erard

5. That's the joy of trying to represent fractions in binary.

6. Take any cheap calculator
Type in 1 ÷ 7 x 7 =
Did you expect to get 1.000000?
You probably got 0.9999997 (the number of 9s may vary).
Same problem of "representation of fractions as a less-than-infinite number of decimals" as above.

Writing from Europe, therefore I use decimal commas instead of decimal points
Not in the UK, we don't!