The mass of a box is $2.3\, kg$. Adding $2.15\, g$ and $12.39\, g$ to it,the total mass is ........ $kg$.

For an experimental expression $y=\frac{32.3 \times 1125}{27.4}$,where all the digits are significant. Then to report the value of $y$,we should write $:-$

If $N_A, N_B$,and $N_C$ are the number of significant figures in $A=0.001204 \ m$,$B=43120000 \ m$,and $C=1.200 \ m$ respectively,then:

Round off the value $2.845$ to three significant figures.

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 $\,s$)

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