If the radius of a sphere is doubled,

Let v1 and v2 be the volumes of the first and second sphere respectively

Radius of the first sphere = r

Radius of the second sphere = 2r

Therefore, $\frac{\text { Volume of first sphere }}{\text { Volume of second sphere }}=\frac{\frac{4}{3} \pi r^{3}}{\frac{4}{3} \pi(2 r)^{3}}$

= 1/8