Explanation:
Let radius of \({}_4B{e^9}\) nuclues be \(r\). Then, radius of germanium \((Ge)\) nucleus will be \(2r\).
Radius of nucleus is given by \(R = {R_0}{A^{1/3}}\)
\(\therefore \frac{{{R_1}}}{{{R_2}}} = {\left( {\frac{{{A_1}}}{{{A_2}}}} \right)^{1/3}} \Rightarrow \frac{r}{{2r}} = {\left( {\frac{9}{{{A_2}}}} \right)^{1/3}}\,\) \(\,\,(\because {A_1} = 9)\)
\( \Rightarrow {\left( {\frac{1}{2}} \right)^3} = \frac{9}{{{A_2}}} \Rightarrow {A_2} = 72\)
Thus, in germanium \((Ge)\) nucleus 72 nucleons are present.