In physics:
x=3/2 x = 1 (significatif digits)
y=x*2 y = 2

z=3/2*2 z=3


GA! I just lost 10% on a quiz for this sort of mistake. Significatif digits are flawed anwyas... Base dependant.

Base 10:

10/4 = 2

Base 2:

1010 / 100 = 10.1 (2.5, more precision! same numbers!)