The volume of a complete sphere is
V = (4/3 π) · (radius)³ .
The arena is not a complete sphere.
It's just half of a sphere.
So its volume is
V = (2/3 π) · (radius)³
= (2/3 π) · (55 m)³
= (2/3 π) · (166,375 m³) .
= 348,454.9852 m³
= 348,454.99 m³ . when rounded
