Finding remainders and assigning variables

This is a flash AS3 related question.

Firstly let me start by saying these forums are great what a wealth of knowledge.

It is time for me to stop looking and start asking I'm afraid.

Please help an old fella out with a taxing question.

I wish to take a number

Example 2.1

And end up with two variables

1st variable containing the whole number and the second with the remainder.

Example

var one = 2

var two = 0.1

I have tried the following

var testnumber = 2.1

var rounded = Math.floor(testnumber);

trace("Rounded number");

trace(rounded );

var answer = testnumber - rounded

trace ("answer");

trace (answer);

but the remainder number comes out with 0.10000000000000009

Is there any way I can make this number become 0.1?

To make matters more complicated I also wish to work with negative numbers.

var testnumber = -1.4

i.e

var one = -1

var two = 0.4

the var testnumber could be anywhere between -10.0 and 50.0

Would this work the same as above if a solution could be found?

Any ideas?

Regards

Adey