The total surface area of a cone whose radius is $\frac{r}{2}$ and slant height is $2l$ is

Find the curved surface area and the total surface area of a cone with radius $3.5 \, cm$ and height $12 \, cm$.

$A$ school provides milk to the students daily in cylindrical glasses of diameter $7\, cm$. If the glass is filled with milk up to a height of $12\, cm$, find how many litres of milk is needed to serve $1600$ students. (in $0.2$)

The radii of five metal spheres are $1\, cm, 3\, cm, 4\, cm, 5\, cm$ and $8\, cm$ respectively. If they are melted and cast into a single large sphere,find the radius of that sphere. Furthermore,if this large sphere is melted and recast into smaller cylinders,each with a radius of $3\, cm$ and a height of $4\, cm$,how many such cylinders can be formed?

Find the volume of a sphere of radius $2.1 \, cm$. (in $cm^3$)

The total surface area of a cube is $96 \, cm^2$. The volume of the cube is (in $cm^3$)