Rules to verify how many significant numbers has in a calculated quantity:

1.  All nonzero digits are significant. As like 457 cm has three significant values; 0.25 g has two significant figures.

2.  Zeros among nonzero digits are significant. As like, 1005 kg has four significant values; 1.03 cm has three significant values.

3.  Zeros to the left of the first nonzero digits in a number are not significant; they merely indicate the position of the decimal point. As like, 0.02g has one important value; 0.0026 cm has two important figures.

4.  When a number ends in zeros that are to the right of the decimal point, they are important. As like, 0.0200g has three important values; 3.0cm has two important figures.