5 significant figures.
2 of them.
12.655 cm rounded to four significant figures is 12.66cm
All three of them are significant figures
102.3 cm
5 significant figures.
There are 4 significant figures in this number.
There are 2 significant figures in this measurement.
4.05 has three (3) significant figures
There are 3 significant figures
None. The abbreviation cm represents one or more centimeters. In your question there are no numbers associated with the cm unit, therefore there are no significant figures.
2 of them.
12.655 cm rounded to four significant figures is 12.66cm
There are two significant figures in the measurement 210 cm.
3 of them.
1730 feet is 52,730.4 cm.
There are four significant figures in 0.00301 cm. The non-zero digits (3 and 1) and zeros between them are all considered significant.