Which is the best method to determine significant numbers?

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

The number of significant figures in the numbers $4.8000 \times 10^{4}$ and $48000.50$ are respectively

The number of significant figures in $3.78 \times 10^{22} \ kg$ is

$A$ cube has a side of length $1.2 \times 10^{-2} \; m$. Calculate its volume.

If the value of resistance is $10.845 \, \Omega$ and the value of current is $3.23 \, \text{A}$,the value of potential with significant figures would be ........... $V$.