$A$ toy is in the form of a cone surmounted on a hemisphere. The radius of the cone as well as the hemisphere is $3.5\, cm$ and the total height of the toy is $15.5\, cm$. Find its total surface area (in $cm^2$).

The surface area of a sphere is $\ldots \ldots$

$A$ cylindrical tank is closed at both the ends by hemispheres. The diameter of the tank is $24 \, cm$ and the total height is $78 \, cm$. How many litres of kerosene can it hold?

Two solid cones $A$ and $B$ are placed in a cylindrical tube as shown in the figure. The ratio of their capacities is $2:1$. Find the heights and capacities of the cones. Also,find the volume of the remaining portion of the cylinder (in $cm^{3}$).

The volume of a cylinder is $550 \, cm^3$ and its radius is $5 \, cm$. Then,its height is ....... $cm$.

From a solid cube of side $7 \, cm$,a conical cavity of height $7 \, cm$ and radius $3 \, cm$ is hollowed out. Find the volume of the remaining solid (in $cm^3$).