How to find the scale factor of 9000 x 6000 drawn as 7.5cm x 5cm

Hey guys,
I guess the question at the top does give it away but can you please explain how to find the scale factor. I'm completely in the dark on this one. Help would be very much appreciated :)

9000/7.5 and 6000/5

12000 is your scale factor

According to me, mathematically, scale factor is the number by which your dimensions must be multiplied to get the new dimension. Intuitively, its like to enlarge or diminish an image every part of it must be expanded or reduced by the same amount or the image would look weird. So,

x*9000=7.5

and

x*6000=5

To find the scale factor both equations should agree and only then one can find the scale factor. For finding it you can use any equation.

x=7.5/9000

x=8.33*(10^-4)

or

x= 0.000833