Since b^2 - 4ac = 9-16 < 0
There is no real root present.
The answer is
![r= \sqrt[3]{GMT^{2}/4 \pi^{2}}](https://tex.z-dn.net/?f=r%3D%20%5Csqrt%5B3%5D%7BGMT%5E%7B2%7D%2F4%20%5Cpi%5E%7B2%7D%7D%20)

Move

to the other side of the equation:

Rearrange:

Since
![x^{3}= \sqrt[3]{x}](https://tex.z-dn.net/?f=%20x%5E%7B3%7D%3D%20%5Csqrt%5B3%5D%7Bx%7D%20%20)
, then
I solved this problem by setting 240/80 equal to x/100 . Once you set them equal to each other, multiply 240 and 100 and divide the product by 80 and you get 300.
It is exponentially each time you are dividing by 4/3