The diameter of a sphere is decreased by $25\%$. By what per cent does its curved surface area decrease (in $\%$)?

The curved surface area of a right circular cylinder of height $14\, cm$ is $88\, cm^2$. Find the diameter of the base of the cylinder.
Assume $\pi = \frac{22}{7}$ unless stated otherwise. (in $, cm$)

Find the cost of digging a cuboidal pit $8 \, m$ long,$6 \, m$ broad,and $3 \, m$ deep at the rate of $Rs. 30$ per $m^3$.

Twenty-seven solid iron spheres,each of radius $r$ and surface area $S$,are melted to form a single sphere with surface area $S^{\prime}$. Find the radius $r^{\prime}$ of the new sphere. (in $r$)

Find the volume of a sphere whose radius is $7 \, cm$. Assume $\pi = \frac{22}{7}$.

$A$ small indoor greenhouse (herbarium) is made entirely of glass panes (including base) held together with tape. It is $30 \, cm$ long,$25 \, cm$ wide and $25 \, cm$ high. What is the area of the glass (in $, cm^2$)?