How many spherical lead shots,each of diameter $4.2 \, cm$,can be obtained from a solid rectangular lead piece with dimensions $66 \, cm \times 42 \, cm \times 21 \, cm$?

The ratio of radii of two spheres is $2:3$. Then,the ratio of their volumes is $\ldots \ldots \ldots \ldots$.

$A$ heap of rice is in the form of a cone of diameter $9 \, m$ and height $3.5 \, m$. Find the volume of the rice. How much canvas cloth is required to just cover the heap?

$A$ cylindrical tank is closed at both the ends by hemispheres. Its radius is $2.1 \,m$ and the total height is $9.2 \,m$. How many litres of petrol can it contain?

The volume of a cone with radius $6 \, cm$ and height $21 \, cm$ is $\ldots \ldots \ldots \, cm^{3}$.

$A$ solid iron cuboidal block of dimensions $4.4 \, m \times 2.6 \, m \times 1 \, m$ is recast into a hollow cylindrical pipe of internal radius $30 \, cm$ and thickness $5 \, cm$. Find the length of the pipe in meters.