The slant height of a cone with radius $6 \, cm$ and height $8 \, cm$ is $\ldots \ldots \ldots \ldots cm$.

$A$ tent is in the shape of a cylinder surmounted by a conical top. If the height and diameter of the cylindrical part are $2.1 \, m$ and $4 \, m$ respectively,and the slant height of the top is $2.8 \, m$,find the area of the canvas used for making the tent. Also,find the cost of the canvas of the tent at the rate of $Rs. \, 500$ per $m^2$. (in $Rs.$) [Use $\pi = \frac{22}{7}$] (Note that the base of the tent will not be covered with canvas.)

$A$ wooden article was made by scooping out a hemisphere from each end of a solid cylinder,as shown in the figure. If the height of the cylinder is $10 \, cm$ and its base radius is $3.5 \, cm$,find the total surface area of the article (in $cm^2$).

Write 'True' or 'False' and justify your answer:
$A$ solid cone of radius $r$ and height $h$ is placed over a solid cylinder having the same base radius and height as that of the cone. The total surface area of the combined solid is $\pi[\sqrt{r^{2}+h^{2}}+3r+2h]$.

Curved surface area of a hemisphere $= \ldots \ldots \ldots . .$

The slant height of a frustum of a cone is $4 \,cm$ and the perimeters (circumference) of its circular ends are $18 \,cm$ and $6 \,cm$. Find the curved surface area of the frustum in $cm^2$.