We have the formula of volume : \(a\cdot a\cdot a\)

Give example a = 5 we have : \(V=a^3=5^3=125\)

Increase 50% side we have : \(V'=\left(150\%\cdot a\right)^3=7,5^3=421,875\)

\(\%V_{increase}=\dfrac{\dfrac{421}{875}}{125}\cdot100\%=337,5\%\)

So the volume increase 337,5-100=237,5%.

Choose C.