Curved surface area of a hemisphere $= \ldots \ldots \ldots$

If the edge of a cube is $12 \, cm$,find its volume (in $cm^3$).

The ratio of radii of two cylinders with equal height is $4:5$. What is the ratio of their volumes?

For a given cylinder,the diameter of the base is $7 \,cm$ and its height is $12 \,cm$. Find the curved surface area of a cylinder (in $cm^2$).

$A$ small village, having a population of $5000$, requires $130\, \text{litres}$ of water per head per day. The village has an overhead cuboidal tank measuring $20\, \text{m} \times 13\, \text{m} \times 10\, \text{m}$. For how many days will the water of this tank last?

Find the surface area of a sphere of diameter $49\, cm$ (in $cm^2$).