How can I find "r" in this equation?

You don’t really need to know much about what this is for, just how the math works, because the square root is annoying me. And crap. . how do I express square root on my keyboard? Oh well, let me explain it best I can.

RPM = square root (RCF/1.119×10^-5 x r)

RPM and RCF are speeds, and r is the radius of the center of the sample to the center of the centrifuge, in centimeters I believe.

I know for a fact that in this centrifuge, 25,000 RCF is equal to 14,500 RPM. So knowing that, I want to find out the radius so that I can figure out how much 20,000 RCF is in RPMs. But when I try to solve for r, I just get a useless, tiny number that is wrong, becuase I end up dividing a small number by a big number. And I tried it also knowing in another centrifuge that 2989.406 = square root (750/1.119×10^-5×7.5). So I tested how I did it by solving for r in there knowing what r was, but I still got a wrong number. So I’m definitely doing something wrong and it probably has to do with how to deal with the square root.