Resizing SWF (scaleX and scaleY) Maths problem

Hello

I need help of any mathematician out there cuz I am not good in it.

I have a swf file that I want to scale down to display inside a parent movie clip.

The parent movie clip dimensions are 425 * 300.

Now if I want to scale down the swf file to half its size I can use this

swf.scaleX = 0.5;
swf.scaleY = 0.5;

But now I want to calculate the value for the scaleX and scaleY so that it comes under the dimension of 425 * 300

I hope I am making sense.

Its basically maths now which i am not good at:(

Thanks in advance.