$1 \text{ litre} = \ldots \ldots \ldots \text{ cm}^3$

In a cylinder,if the radius is doubled and the height is halved,the curved surface area will be:

The length,breadth,and height of a cuboid are $20\, cm$,$15\, cm$,and $12\, cm$ respectively. Find its total surface area (in $cm^2$).

The ratio of the curved surface area and the total surface area of a cylinder is $2: 5$. Find the ratio of the radius and height of the cylinder.

The curved surface area of a cylinder is $1320 \, cm^2$. If its height is $30 \, cm$,find its diameter (in $cm$).

$30$ circular plates,each of radius $14\,cm$ and thickness $3\,cm$,are placed one above the other to form a cylindrical solid. Find:
$(i)$ the total surface area
$(ii)$ the volume of the cylinder so formed.