Lateral surface area of a cuboid $= \ldots \ldots \ldots$

The radius of a cone is $5 \, cm$ and slant height is $9 \, cm$. The total surface area of the cone is $\ldots \ldots \ldots \, cm^2$.

State whether the following statement is True or False and justify your answer:
$A$ cone,a hemisphere,and a cylinder stand on equal bases and have the same height. The ratio of their volumes is $1: 2: 3$.

The surface area of a sphere and the curved surface area of a hemisphere are equal. Find the ratio of their radii.

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 surface area of a sphere with a diameter of $21\, cm$ (in $cm^2$).