What is the number of significant figures in $11.118 \times 10^{-6} \ V$?

The length of the side of a cube is $1.2 \times 10^{-2} \ m$. Its volume up to correct significant figures is

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 $\,s$)

The result after adding $3.8 \times 10^{-6}$ and $4.2 \times 10^{-5}$ with due regard to significant figures is:

$5.74 \; g$ of a substance occupies $1.2 \; cm^3$. Express its density (in $g/cm^3$) by keeping the significant figures in view.