Answer:
1. 3 (leading zeros are NOT significant, and trailing zeros in a whole number with no decimal shown are also NOT significant)
2.7 (trailing zeros in a whole number with no decimal shown are also NOT significant), and zeros between non-zero digits are significant)
3. 7 (zeros between non-zero digits are significant)
4.13 (zeros between non-zero digits are significant))
5. 1 (railing zeros in a whole number with no decimal shown are NOT significant)
you may try reading the rules for significant figures.
