"Changing the units of measurement does not change the number of significant figures." Explain with an example.

$A$ student measuring the diameter of a pencil of circular cross-section with the help of a vernier scale records the following four readings: $5.50\, mm, 5.55\, mm, 5.45\, mm, 5.65\, mm$. The average of these four readings is $5.5375\, mm$ and the standard deviation of the data is $0.07395\, mm$. The average diameter of the pencil should therefore be recorded as:

If the length of a rectangular plate is $1.5\, cm$ and the width is $1.203\, cm$, then its area is ............ $cm^2$.

The radius of the Earth is $6371 \ km$ and the radius of its orbit around the Sun is $149 \times 10^6 \ km$. The order of magnitude of the diameter of the orbit is greater than that of the Earth by

The volume of a sphere is $1.76 \ cm^3$. The volume of $25$ such spheres,taking into account significant figures,is:

Each side of a cube is measured to be $7.203 \; m$. What are the total surface area and the volume of the cube to appropriate significant figures?