Step-by-step explanation:
the area of the curved surface is
pi×radius×slanted height
the slanted height is calculated by Pythagoras :
(slanted height)² = (inner height)² + radius²
12320 cm² = pi×radius×sqrt((inner height)² + radius²)
to get rid of the square root we square everything :
151,782,400 = pi²×56²×((inner height)² + 56²)
4,903.945288... = (inner height)² + 3136
(inner height)² = 1,767.945288...
inner height = 42.04694149... cm
