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

The radii of a frustum of a cone are $28 \, cm$ and $7 \, cm$ and its height is $72 \, cm$. Find its curved surface area,total surface area,and volume.

$A$ cylinder is closed at both ends by $12 \, cm$ high cones. The radius of the cylinder is $5 \, cm$ and the total height of the article is $41 \, cm$. Find the total surface area of the article. $(\pi = 3.14)$ (in $cm^2$)

The radii of two $10 \, cm$ high metallic cylinders are $3.5 \, cm$ and $7 \, cm$. These cylinders are melted and recast to produce a cylinder with height $50 \, cm$. Find the radius of this new cylinder (in $cm$).

The base of a cone with radius $6 \, cm$ and height $8 \, cm$ is hemispherical. Find the curved surface area and the volume of the solid. $(\pi = 3.14)$

$A$ canal is $300 \,cm$ wide and $120 \,cm$ deep. The water in the canal is flowing with a speed of $20 \,km/h$. How much area will it irrigate in $20 \,minutes$ if $8 \,cm$ of standing water is desired? (in $hectares$)