Properties If a prism whose night section is a regular polygon is inscribed in or cir- cumscribed about a circular cylinder, and if the number of sides of the right section of the prism is indefinitely increased in such a way that ev- ery side approaches zero , the volume of the cylinder is the limit of the volume of the prism ;the lateral area of the cylinder is the limit of the lat- eral area of the prism _:the perimeter of a base of the cylinder is the limit of the perimeter of a base of the prism . Formulas The lateral area of a circular cylinder is equal to the product of the perime- ter of a right section and an element Lateral area = perimeter of right section X element . S = pke The volume of a circular cylinder is equal to the product of either a right section and an element or the base and the altitude V o l u m e = base X altitude V = B h . Volum e = right section X lateral edge . V = K 8. Example 7. A pole in the form of a circular cylinder of altitude 13 ft. and diameter of right section 0.4 It. has a base whose largest dimension is 0.5 ft. If the pole rolls until it has covered an area of level ground, equal to that of one acre, how many revolutions will it make