The difference of the external and internal radius forms wall thickness of a cylinder ie. The formula for the volume of a cylinder circular prism is derived from the volume of a prism where r is the radius and h is the heightlength. Like prisms the volume is found by multiplying the area of one end of the cylinder base by its height.
To get the area of the base you need its radius.
The a b part of the sum is actually working out the area of the base before the 3rd multiplication by the height c. Volume of a cylinder ph r12 r22 Where r 1 external radius and r 2 internal radius of a cylinder. Lets solve a few example problems about volume of cylinders. The formula for the volume of a cylinder circular prism is derived from the volume of a prism where r is the radius and h is the heightlength.