How many significant digits does the number 0.0034 have?
Two significant digits (3 and 4)
For zeros, the rule of significant digits can be tricky, but here are the general rules:
In this case, there are three significant digits: 607
This number contains four significant digits (all the zeros are significant because they come after a non-zero digit and are after the decimal point).
And this notation is not seen as often, but I'll include it anyway:
Since the first zero has a bar over it, then this number has two significant digits (the last zero is not a significant digit- there is no bar over it).