Keeping the significant figures in view, the sum of the physical quantities $52.01 \ m$, $153.2 \ m$, and $0.123 \ m$ is: (in $m$)

Each side of a metallic cube of mass $5.580 \text{ kg}$ is measured to be $9.0 \text{ cm}$. Keeping the significant figures in view, the density of the material of the cube can be best expressed as $X \times 10^3 \text{ kg m}^{-3}$, where the value of $X$ is:

Time periods of oscillation of the same simple pendulum measured using four different measuring clocks were recorded as $4.62 \,s, 4.632 \,s, 4.6 \,s$ and $4.64 \,s$. The arithmetic mean of these readings in correct significant figures is: (in $\,s$)

$A$ body of mass $m = 3.513\ kg$ is moving along the $x$-axis with a speed of $5.00\ ms^{-1}$. The magnitude of its momentum is recorded as ........ $kg\ m/s$.

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

$A$ length of $5.997 \ m$ rounded off to three significant figures is written as .......... $m$.