Area calculation - round decimals error

[nejcek74]

This is something that bothers mi for long time: I have to exact sized* rooms, but than, depends on the rounding decimals value I got unexpected results.
Area of 13.65000 m2 is once rounded into 13.7 m2 and once into 13.6 m2?
Any insight into this? Why? How to avoid, etc?

*I am obsessed with exact measurement and orthogonal drawing

[Barry Kelly]

Maybe the rooms are not exactly 13.650000
The first could actually be 13.6500001 which will round to 13.650000 and 13.7
The second could be 13.6499999 which will round to 13.650000 and 13.6

If my math is correct?

Barry.

[nejcek74]

Probably, but it's kind of hard to locate the mistake, because also all the coordinates in tracker shows full numbers.
- it happened by copying whole plan (while making variants of original plan)
- changes of corner points with absolute coordinates (relative coordinates in tracker switched off) doesn't help
I draw it anew, but I am looking how to avoid such situations in the future. Or at least how to find where the error is.
Yes, I know that culprit is probably floating point (im)precision