The K&R 'C' manual (aka The Bible) explicitly warns about this, and advizes the use of fuzzy checks, i.e.:
code:
BAD  : If $x = 0
 
GOOD : If ($x>=-0.01 AND $x <=0.01)
Or whatever your margin of error is.

As the guys say, is better to stick to integer maths and convert. Your first example would become:
code:
Break ON
For $x = 11 To 21
   Cdbl($x)/10 ?
Next