If the radius of a sphere is doubled, how many times does its volume becomes ?

Answer: Option D

Let the original radius be r
Then, original volume = $$\frac{4}{3}\pi r^3$$
New area = 2r
∴ New volume :
$$\begin{array}{rl}& =\frac{4}{3}\pi {\left(2r\right)}^3\\ & =8\times \frac{4}{3}\pi r^3\\ & =8\times \text{Original volume}\end{array}$$