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

$A$ milk container of height $16 \, cm$ is made of metal sheet in the form of a frustum of a cone with radii of its lower and upper ends as $8 \, cm$ and $20 \, cm$ respectively. Find the cost of milk at the rate of $Rs. \, 22$ per $litre$ which the container can hold. (in $Rs.$)

Rachel,an engineering student,was asked to make a model shaped like a cylinder with two cones attached at its two ends by using a thin aluminium sheet. The diameter of the model is $3\, cm$ and its total length is $12\, cm$. If each cone has a height of $2\, cm$,find the volume of air contained in the model that Rachel made. (Assume the outer and inner dimensions of the model to be nearly the same.) Unless stated otherwise,take $\pi = \frac{22}{7}$. (in $cm^3$)

The volume of a cone with radius $5 \, cm$ and height $12 \, cm$ is ........ $\pi \, cm^{3}$.

The $CSA$ and the volume of a cylinder are numerically equal. Then,its radius is $\ldots \ldots \ldots \ldots$ units.

The base of a cone is hemispherical. The radius of the cone is $15 \, cm$ and the total height of the solid is $55 \, cm$. Find the volume of this solid (in $cm^3$).