$A$ rectangular water tank is $80 \, m \times 40 \, m$. Water flows into it through a pipe with an opening area of $40 \, cm^2$ at a speed of $10 \, km/h$. By how much will the water level in the tank rise in half an hour (in $cm$)?

$A$ $1 \, m^3$ of metal weighing $90 \, Kg$ is rolled into a square bar $9 \, m$ long. An exact cube is cut off from the bar. How much does it weigh? (in $kg$)

The volume of a cube is $729 \, cm^3$. The total surface area of the cube is ........ $cm^2$.

$A$ conical cup is filled with ice cream. The ice cream forms a hemispherical shape on its open top. The radius of the hemispherical part is $7 \, cm$. The radius of the hemispherical part equals the height of the cone. Then the volume of the ice cream is $...... cm^3$. $\left[\pi=\frac{22}{7}\right]$

$2$ cans have the same height equal to $21\, cm$. One can is cylindrical,the diameter of whose base is $10\, cm$. The other can has a square base of side $10\, cm$. What is the difference between their capacities? (in $cm^3$)

$A$ right circular cylinder has a height of $18 \, cm$ and a radius of $7 \, cm$. The cylinder is cut into three equal parts by $2$ cuts parallel to the base. What is the percentage increase in the total surface area (in $\%$)?