To find side $ a $ use formula:

$$ V = \dfrac{ a ^{ 2 } \cdot h }{ 3 } $$

After substituting $V = 15000\, \text{cm}$ and $h = 50\, \text{cm}$ we have:

$$ 15000\, \text{cm} = \dfrac{ a ^{ 2 } \cdot \left( 50\, \text{cm} \right)^{4} }{ 3 } $$$$ 15000\, \text{cm} \cdot 3 = a ^{ 2 } \cdot \left( 50\, \text{cm} \right)^{4} $$$$ 45000\, \text{cm} = 50\, \text{cm} \cdot a ^{ 2 } $$$$ a ^{ 2 } = \dfrac{ 45000\, \text{cm}}{ 50\, \text{cm} } $$$$ a ^{ 2 } \approx 286.4782 $$$$ a \approx \sqrt{ 286.4782 } $$$$ a \approx 16.9257 $$

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