int((9.2-9.0)*10) is 1, int((9.21-9.0)*10) is 2, why?

[bcm]

On Sep 5, 9:29 pm, John Machin <sjmac... at lexicon.net> wrote:
> On Sep 5, 11:12 pm, bcm <bluecrysta... at gmail.com> wrote:
>
>
>
> > Python 2.5.2 (r252:60911, Feb 21 2008, 13:11:45) [MSC v.1310 32 bit
> > (Intel)] on win32
> > The following line of code describes an  funny question：>>> int((9.2-9.0)*10)
> > 1
> > >>> int((9.21-9.0)*10)
> > 2
> > >>> int((9.1-9.0)*10)
> > 0
> > >>> int((9.11-9.0)*10)
> > 1
> > >>> int((8.2-8.0)*10)
> > 1
> > >>> int((8.23-8.0)*10)
>
> > 2
>
> > why? anybody can explain it?
>
> Try looking one step at a time:>>> 9.2
>
> 9.1999999999999993
>
> That wasn't hard, was it? Do you need any further explanation? If so,
> look here:http://docs.python.org/tut/node16.html

thanks a lot, i am really really stupid ~*v*~