1. There are 4 significant figures.
2. There are 3 significant figures.
3. There are 3 significant figures - in this case the zero after the decimal counts.
4. There are certainly 2 significant figures (25). The two zeros would most likely not be considered significant.
5. There are 2 significant figures (70)
6. 4 significant figures.
7. 2 significant figures (67)
8. 3 significant figures (602 are significant figures - the power on the ten doesn't count)