$A$ cylinder is closed at both the ends by $18\, cm$ high cones. The radius of the cylinder is $7\, cm$ and the total height of the solid is $64\, cm$. Find the volume of this solid (in $cm^3$).

Write 'True' or 'False' and justify your answer:
If a solid cone of base radius $r$ and height $h$ is placed over a solid cylinder having the same base radius and height as that of the cone,then the curved surface area of the shape is $\pi r \sqrt{h^{2} + r^{2}} + 2 \pi r h$.

$A$ cylindrical tank with radius $8.4 \,cm$ is closed at one end by a hemisphere. If the total height of the tank is $52.8 \,cm$,how many litres of petrol can it contain (in $.088$)? (in $litres$)

$A$ cylinder is closed at both ends by hemispheres. The radius of the cylinder is $21 \, cm$ and the total height of the article is $92 \, cm$. Find the total surface area of the article (in $cm^2$).

$A$ cylindrical tank is closed at both the ends by hemispheres. Its radius is $2.1 \,m$ and the total height is $9.2 \,m$. How many litres of petrol can it contain?

Two cones with the same base radius $8\, cm$ and height $15\, cm$ are joined together along their bases. Find the surface area of the shape so formed. (in $cm^2$)