$A$ cylindrical pillar is $50 \, cm$ in diameter and $3.5 \, m$ in height. Find the cost of painting the curved surface of the pillar at the rate of $Rs. \, 12.50$ per $m^2$. $\left[ \text{Assume } \pi = \frac{22}{7} \right]$

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 $, cm$)

Savitri had to make a model of a cylindrical kaleidoscope for her science project. She wanted to use chart paper to make the curved surface of the kaleidoscope (see figure). What would be the area of chart paper required by her,if she wanted to make a kaleidoscope of length $25\, cm$ with a $3.5\, cm$ radius (in $, cm^{2}$)? You may take $\pi=\frac{22}{7}$.

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

The paint in a certain container is sufficient to paint an area equal to $9.375 \,m^2$. How many bricks of dimensions $22.5 \,cm \times 10 \,cm \times 7.5 \,cm$ can be painted out of this container?

Find the surface area of a sphere of radius $7 \, cm$. (in $, cm^{2}$)