\(x \propto \,\,\frac{1}{{\sqrt P }}\,\,\,\,\,\,\,\,\,\,\,\,x\,\, \propto \,\,\sqrt V \)
\(\frac{{{x_2}}}{{{x_1}}} = \frac{{\sqrt {16V} }}{{\sqrt V }}\,\,\,\,\,\,\,\frac{{{x_2}}}{{{x_1}}} = \frac{{4\sqrt V }}{{\sqrt V }} \Rightarrow \,{x_2} = 4{x_1}\)