How many significant figures are in 0.0032 mm

In a number, to determine the number of significant figures following 3 rules are used:  

(1) The digits which are non-zero are always significant. (2) Any zeros between two digits which are non-zero are significant. (3) In the decimal portion, trailing zeros are significant.  

The number is 0.0032 nm, it has two non-zero digits and the zeros are not trailing zeros.

Therefore, there are only 2 significant figures (underlined): 0.0032.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it