How many significant digits are there in these numbers

3.80 x 10-5

and:

7.6 x 103
7.60 x 103
7.600 x 103

Thanks so much

Remember the rules of significant digits:

1) All non-zero digits are significant.
2) All zeros to the left of all non-zero digits are not significant.
3) All zeros between two non-zero digits are significant.
4) Zeros to the right of all non-zero digits may be significant. For scientific notation, all zeros to the right are significant.

3.80 x 10^-5 has 3 significant digits.
7.6 x 10^3, 7.60 x 10^3and 7.600 x 10^3 have 2, 3 and 4 respectively.