Conditional formatting not working with cell

[Luciane]

Hi

New here and was wondering if someone could help me with formatting of cells on a spreadsheet.

I am running into problems when i try a make a cell go red when a value has been worked out with a formula.

I am wanting the cell to go red if its +/- 0.30 but for some reason when the value returns +/- 0.31 its still green but then turns red when it goes to +/- 0.32.
The formatting seems to work fine if you just type 0.31 but for some reason when the formula works it out it doesn't like it.
Sorry i am new to this sort of stuff and its probably pretty basic when you know how :P

Thanks in Advance

[bebo021999]

It is called "floating points" in Excell (try to google it to study)
0.31 actually is 0.30999999999999
Try to test by input 28.31 in K3; 28 in K4 then K5=K3-K4, increase decimal enought to see its actual value is 0.3099999999999
It would not happen to other value,i.e, 0.32
to prevent it, in conditional formating: try = -0.30999999999 instead of -0.31

[Luciane]

That worked perfectly.

Thanks very much and will do some more research into floating points