A closed cylinder of given volume will have least surface area when the ratio of its height and base radius is

A closed clylinder of given volume will have least surface when height (h) and radius (r) are related as

Show that a closed cylinder of a given volume will have its least surface when its height is equal to its diameter.

Show that the height of a closed right-circular cylinder of given volume and least surface area is equal to its diameter.

Show that the height of a closed right circular cylinder of a given volume and least surface area is equal to its diameter.

Show that a cylinder of given volume, open at the top, has minimum total surface area if its height is equal to radius of the base.

Show that a cylinder of a given volume which is open at the top has minimum total surface area, when its height is equal to the radius of its base.

Show that a cylinder of a given volume which is open at the top has minimum total surface area, when its height is equal to the radius of its base.