100, 101, 102, etc

is there a rule of whether or not to say ''and'' when saying these numbers 101, 102, one hundred and one, one hundred one?

Whichever. My math teacher told us to leave out the "and", but people say it either way.

i generally say 1hundred and 1, since it flows better other wise it would be more like 1hundred, pause, 1

You aren't supposed to say the "and" because then it means you are saying a decimal, according to my old math teacher.

Most people nowadays say "point" when saying decimals.
0.35= Nought point three five
3.62= Three point six two

"And" is still used but never in the above construction. If you want to use "and", you must say...
3.62= Three and sixty-two *hundredths*

What's the world comming to when maths teachers tell kids how to speak English ... still, would it be any less rich coming from an English teacher?

May I politely suggest to you, Andrea and Californian, that you should feel free to tell your maths teachers that they don't know what they're talking about.

In Aussie you always put the "and" in 101, 102, 103, etc. you never use it when saying a decimal (well, if it were 101.3 or something, that's a different story).

It's a question of dialect not mathematics. In Canadian & American English, as far as I know, it's optional. In Australian English, it's mandatory. I'm guessing that the British, Kiwi, S. African and Irish cases are the same as the Aussie one.