$V_1=\frac{1}{3}\cdot 5^2\cdot 10=\frac{1}{3}\cdot 25\cdot 10=\frac{250}{3}$  

$V_2=\frac{1}{3}\cdot {10}^2\cdot H=\frac{100}{3}H$  

$\frac{250}{3}=\frac{100}{3}H\mid \cdot 3$  

$250=100H\mid :100$  

$2,5=H$