The addition of three masses $1.6 \,g$,$7.32 \,g$,and $4.238 \,g$,expressed to the proper number of decimal places,is ....... $g$.

The number of significant figures in $6.25 \times 10^5$ is

Assertion $(A)$: The number $0.00764$ has three significant figures.
Reason $(R)$: If the number is less than $1$,the zeros on the right of the decimal point but to the left of the first non-zero digit are not significant.

State the number of significant figures in the following:
$(a)$ $0.007 \;m^{2}$
$(b)$ $2.64 \times 10^{24} \;kg$
$(c)$ $0.2370 \;g \;cm^{-3}$
$(d)$ $6.320 \;J$
$(e)$ $6.032 \;N \;m^{-2}$
$(f)$ $0.0006032 \;m^{2}$

The radius of a circle is $2.12 \ m$. Its area according to the rule of significant figures is ......... $m^2$.

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 $\,s$)