Choose the correct answer of the following question:
If the radius of a sphere becomes 3 times, then its volume will become
(a) 3 times (b) 6 times (c) 9 times (d) 27 times
Let the radius of the given sphere and that of the new sphere be $r$ and $R$, respectively;
Also, the volume of the given sphere and that of the new sphere be $v$ and $V$, respectively.
We have,
$R=3 r \quad \ldots \ldots(\mathrm{i})$
Now,
$\frac{\text { Volume of the new sphere }}{\text { Volume of the given sphere }}=\frac{\left(\frac{4}{3} \pi \mathrm{R}^{3}\right)}{\left(\frac{4}{3} \pi \mathrm{r}^{3}\right)}$
$=\left(\frac{R}{r}\right)^{3}$
$=\left(\frac{3 r}{r}\right)^{3} \quad[\operatorname{Using}(\mathrm{i})]$
$=3^{3}$
$=27$
Hence, the correct answer is option (d).