The surface area of a sphere with radius $7\,cm$ is $\ldots \ldots \ldots \ldots cm ^{2}$.

$A$ bucket is in the form of a frustum of a cone and holds $28.490 \, \text{litres}$ of water. The radii of the top and bottom are $28 \, \text{cm}$ and $21 \, \text{cm}$, respectively. Find the height of the bucket. (in $\text{cm}$)

The base of a cone with radius $15 \, cm$ and height $20 \, cm$ is hemispherical. Find the total surface area of this article. $(\pi = 3.14)$ (in $cm^2$) (in $.5$)

......... is a unit of volume.

$A$ 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?

$A$ cone of radius $8 \, cm$ and height $12 \, cm$ is divided into two parts by a plane through the mid-point of its axis parallel to its base. Find the ratio of the volumes of the two parts.