How do you round 12.555km to four significant figures?

Answer 1

All of those figures are significant. If you want to round it to 2 sig figs, that would be 13.

Answer 2

To round 12.555 km to four significant figures, you would keep the first four non-zero digits, which are 12.56 km since the next digit (5) is greater than 5.

Answer 3

12.56 km