Write 'True' or 'False' and justify your answer:
Two identical solid hemispheres of equal base radius $r \text{ cm}$ are joined together along their bases. The total surface area of the resulting solid is $6 \pi r^{2}$.

The volume of a sphere is $4.5 \pi \, cm^3$. Then,its diameter is $\ldots \ldots \ldots \ldots cm$.

The area of the base of a cone is $60 \, cm^{2}$ and its height is $15 \, cm$. Then,the volume of the cone is $\ldots \ldots \ldots \, cm^{3}$.

$A$ mason constructs a wall of dimensions $270 \,cm \times 300 \,cm \times 350 \,cm$ with bricks each of size $22.5 \,cm \times 11.25 \,cm \times 8.75 \,cm$. If $\frac{1}{8}$ of the total volume of the wall is occupied by mortar,find the number of bricks used to construct the wall.

The radii of a frustum of a cone are $10\,cm$ and $7\,cm$. If its height is $4\,cm$, then its curved surface area is $\ldots \ldots \ldots \,cm^2$. (in $\pi$)

Total surface area of a cylinder $= \dots$