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.
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.
It has 2 significant figures. However, the fact that it is given as 2300 mm and not as 230 cm suggests that it is, in fact significant to 4 figures.