The length,breadth,and height of a cuboidal box are $30 \, cm$,$20 \, cm$,and $8 \, cm$ respectively. Find the lateral surface area of the cuboidal box (in $cm^2$).

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 $\pi=\frac{22}{7}$.

In a cylinder,if the radius is doubled and the height is halved,the curved surface area will be:

State whether the following statement is True or False and justify your answer: In a right circular cone,the height,radius,and slant height do not always form the sides of a right triangle.

$A$ lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil is $7 \,mm$ and the diameter of the graphite is $1 \,mm$. If the length of the pencil is $14 \,cm$,find the volume of the wood and that of the graphite. (in $,cm^3$)

$A$ metal sphere of radius $20\, cm$ is melted and then cast into small hemispheres each of radius $5\, cm$. Find the number of hemispheres thus obtained (in balls).