V=S $\pi \times {{r}^{2}}\times h=2\pi \times r\times h+2\times \pi \times {{r}^{2}}$ $r=10\Rightarrow 100\pi h=20\pi h+200\pi \Rightarrow 80\pi h=200\pi $ $\Rightarrow 80h=200\Rightarrow h=\frac{200}{80}=2/5$