Find the surface area of a sphere of diameter $49\, cm$ (in $cm^2$).

The radii of three metal spheres are $3 \,cm, 4 \,cm$ and $5 \,cm$ respectively. They are melted into a single solid sphere. Find the radius of the new solid sphere (in $cm$).

The dimensions of a cuboid are in the ratio of $4: 3: 1$. If its total surface area is $3800 \, cm^{2}$,then find its volume in $cm^{3}$.

The lateral surface area of a cube is $256 \, m^2$. The volume of the cube is (in $m^3$)

The ratio of the radius and slant height of a cone is $3:5$ and its curved surface area is $423.9 \, cm^2$. Find its volume. $(\pi = 3.14)$ (in $cm^3$)

Find the total surface area of a hemisphere of radius $42 \, cm$. (in $cm^2$)