Lateral surface area of a cuboid $= \ldots \ldots \ldots$

The diameter of a solid hemisphere is $21 \, cm$,then its volume is $\ldots \ldots \ldots \, cm^3$.

Find the curved surface area of a cone with radius $7 \, cm$ and height $24 \, cm$. (in $cm^2$)

The surface area of a sphere is $7850 \, cm^2$. Find its radius in $cm$. (Use $\pi = 3.14$)

$A$ small village,having a population of $5000$,requires $75$ litres of water per head per day. The village has an overhead tank of measurement $40 \, m \times 25 \, m \times 15 \, m$. For how many days will the water of this tank last?

The length and breadth of a cuboid are $30\, cm$ and $25\, cm$. If the total surface area of the cuboid is double the lateral surface area of the cuboid,find its height and volume.