$${\mathtt{V}} = {\frac{{\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}{\mathtt{\,\times\,}}{{\mathtt{r}}}^{{\mathtt{3}}}}{{\mathtt{3}}}}$$
$${{\mathtt{r}}}^{{\mathtt{3}}} = {\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{V}}}{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}\right)}}$$ => $${\mathtt{r}} = {\sqrt[{{\mathtt{{\mathtt{3}}}}}]{{\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{V}}}{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}\right)}}}}$$
$${\sqrt[{{\mathtt{{\mathtt{3}}}}}]{{\frac{{\mathtt{3}}}{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}\right)}}}} = {\mathtt{0.620\: \!455\: \!356\: \!763\: \!528}}$$
$${\mathtt{r}} = {\mathtt{0.620\: \!455}}{\mathtt{\,\times\,}}{\sqrt[{{\mathtt{{\mathtt{3}}}}}]{{\mathtt{V}}}}$$
.$${\mathtt{V}} = {\frac{{\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}{\mathtt{\,\times\,}}{{\mathtt{r}}}^{{\mathtt{3}}}}{{\mathtt{3}}}}$$
$${{\mathtt{r}}}^{{\mathtt{3}}} = {\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{V}}}{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}\right)}}$$ => $${\mathtt{r}} = {\sqrt[{{\mathtt{{\mathtt{3}}}}}]{{\frac{{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{V}}}{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}\right)}}}}$$
$${\sqrt[{{\mathtt{{\mathtt{3}}}}}]{{\frac{{\mathtt{3}}}{\left({\mathtt{4}}{\mathtt{\,\times\,}}{\mathtt{3.14}}\right)}}}} = {\mathtt{0.620\: \!455\: \!356\: \!763\: \!528}}$$
$${\mathtt{r}} = {\mathtt{0.620\: \!455}}{\mathtt{\,\times\,}}{\sqrt[{{\mathtt{{\mathtt{3}}}}}]{{\mathtt{V}}}}$$