The height of a cylinder is decreased by $8 \%$,keeping its radius unchanged. What is the percentage change in its volume?

The diameter and slant height of a conical tomb are $28\, m$ and $50\, m$,respectively. The cost of whitewashing its curved surface at the rate of $80$ paise per $m^2$ is (in $Rs.$):

$A$ 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 $cm$)?

An inverted conical shaped vessel is filled with water to its brim. The height of the vessel is $8\, cm$ and the radius of the open end is $5\, cm$. When a few solid spherical metallic balls,each of radius $\frac{1}{2}\, cm$,are dropped into the vessel,$25\%$ of the water overflows. The number of balls is:

$A$ tank $3\, m$ long,$2\, m$ wide and $1.5\, m$ deep is dug in a field $22\, m$ long and $14\, m$ wide. If the earth dug out is evenly spread out over the field,the level of the field will rise by nearly (in $cm$)

The slant height of a right circular cone is $10 \, m$,and its height is $8 \, m$. Find the area of its curved surface (in $\pi \, m^2$).