Significant Figures: Any Values

When counting significant figures,
1. All non-zero digits count
(ex: 21.3 has 3 sig figs)
2. Zeros between non-zero's count
(ex: 20.3 has 3 sig figs)
3. Zeros at the beginning (left) of a value NEVER count.
(ex: 0.000456 has 3 sig figs)
4. Zeros at the end (right) of a value count IF there is a
decimal point in the value.
(ex: 560. & 0.00400 have 3 sig figs)
ALL RULES APPLY TO ALL VALUES.
3.