Find the volume of a sphere of radius $2.1 \, cm$. (in $cm^3$)

Find the volume of a sphere with radius $2.1 \, m$ (in $m^{3}$).

The radii of five metal spheres are $1\, cm, 3\, cm, 4\, cm, 5\, cm$ and $8\, cm$ respectively. If they are melted and cast into a single large sphere,find the radius of that sphere. Furthermore,if this large sphere is melted and recast into smaller cylinders,each with a radius of $3\, cm$ and a height of $4\, cm$,how many such cylinders can be formed?

Find the surface area of a sphere of radius $30 \, cm$ $(\pi = 3.14)$ (in $cm^2$).

The radius of the base of a cone is $7 \, cm$ and its height is $30 \, cm$. Find the volume of a cone (in $cm^3$).

Write True or False and justify your answer in each of the following: $A$ cylinder and a right circular cone have the same base and the same height. The volume of the cylinder is three times the volume of the cone.