There is a conical metal part with a bottom diameter of 6 decimeters and a height of 1.5 meters. Now it is melted and made into a cylinder with the same bottom. The height of this cylinder is: 1.5× 1/3=0.5 (m).

There is a rectangular iron sheet with a length of 12.56 decimeters and a width of 5 decimeters as the side of the cylindrical bucket. If it is to maximize its volume, it must be equipped with a bottom, at least: (12.56 ÷ 3.14 ÷ 2) 2× 3.14 =12.56 (square decimeter).