how many significant figures does the following number have? 0.000310

Question

anonymous · Answer

3

anonymous · Answer

what would make it 3

anonymous · Answer

Any digit that is not 0 is a significant digit.
Leading zeros are insignificant.  They are necessary to give us an order of magnitude (0.1 vs 0.01 vs 1... all have 1 significant digit).  

That leaves us with 310.

The last 0 isn't necessary.  If we wanted only 2 significant digits, we'd just write 0.00031.  The fact that it was written means it is a significant digit.

anonymous · Answer

There are many different rules regarding significant digits and many caveats.
For example 100 could have 1, 2, or 3 significant digits.  It's ambiguous.  That's why we use scientific notation, in which only significant digits are written.