Image caption, ...you've done it! The sectors rearranged into the rectangle show the area of the curved surface of the cone = π × radius × slant length.

8 An open metallic bucket is in the shape of a frustum of a cone, mounted on a hollow cylindrical base made of the same metallic sheet. The surface area of the metallic sheet used is equal to ...

Image caption, ...you've done it! The sectors rearranged into the rectangle show the area of the curved surface of the cone = π × radius × slant length.