If the edge of a cube is $7\, cm$,find its total surface area in $cm^2$.

The diameters of two spheres are in the ratio $3: 5$. What is the ratio of their volumes?

Write True or False and justify your answer in each of the following: If a sphere is inscribed in a cube,then the ratio of the volume of the cube to the volume of the sphere will be $6: \pi$.

$A$ hemispherical metallic bowl is made of steel,$0.2 \, cm$ thick. The inner radius of the bowl is $4 \, cm$. Find the outer curved surface area of the bowl (in $cm^2$).

Write True or False and justify your answer in each of the following: If the radius of a right circular cone is halved and height is doubled,the volume will remain unchanged.

In $\Delta ABC$,$\angle B = 90^{\circ}$,$AB = 6.3 \, cm$,and $BC = 8.4 \, cm$. If the triangle is revolved about the side $AB$,find the volume of the cone so obtained. Similarly,if the triangle $ABC$ is revolved about the side $BC$,find the volume of the cone so obtained.