بنابر رابطهٔ ظرفيت خازن داريم:
$C=\kappa {{\varepsilon }_{{}^\circ }}\frac{A}{d}\Rightarrow \frac{{{C}_{2}}}{{{C}_{1}}}=\frac{{{\kappa }_{2}}}{{{\kappa }_{1}}}\times \frac{{{A}_{2}}}{{{A}_{1}}}\times \frac{{{d}_{1}}}{{{d}_{2}}}$
$\xrightarrow[{{A}_{2}}=\frac{1}{2}{{A}_{1}},{{d}_{2}}=3{{d}_{1}}]{{{\kappa }_{1}}=1,{{\kappa }_{2}}=4/5}\frac{{{C}_{2}}}{{{C}_{1}}}=4/5\times \frac{1}{2}\times \frac{1}{3}=\frac{3}{4}$