[tex]\displaystyle\bf\\Vp = 50\times40\times100=2000\times100=200000~cm^3\\\\Vc=Vp=200000~cm^3\\\\mc=\sqrt{Vc}=\sqrt[\b3]{\bf200000}=\sqrt[\b3]{\bf1000\times200}=\\\\=\sqrt[\b3]{\bf1000\times8\times25}=10\times2\times\sqrt[\b3]{\bf25}= \boxed{\bf20\sqrt[\b3]{\bf25}~cm}[/tex]
