The diameter of a metallic ball is $4.2\, cm$. What is the mass of the ball,if the density of the metal is $8.9\, g/cm^3$ (in $, g$)?

$A$ 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 $,cm^3$)

Find the amount of water displaced by a solid spherical ball of diameter $28 \, cm$.

Find the total surface area of a cone,if its slant height is $21 \, m$ and diameter of its base is $24 \, m$. (Take $\pi = \frac{22}{7}$) (in $, m^2$)

$A$ cuboidal water tank is $6 \,m$ long,$5 \,m$ wide and $4.5 \,m$ deep. How many litres of water can it hold (in $,l$)? $(1 \,m^3 = 1000 \,l)$

Find the surface area of a sphere with a diameter of $3.5 \, cm$. Assume $\pi = \frac{22}{7}$. (in $, cm^2$)