How many significant figures are in the measurement 0.0105 km?
The first and most important thing to notice here is that your measurement contains two non-zero digits,
As you know, all non-zero digits are significant, so right from the start you know that your measurement contains at least two significant figures
#0.0color(purple)(1)0color(purple)(5) ->#two non-zero digits
Now, the zero that precedes the decimal point is not significant because it acts as a placeholder zero for a number that is smaller than
The same can be said for the zero that follows the decimal point. Once again, this zero is not significant because the number is smaller than
Finally, the zero that follows
All sandwiched zeroes are significant, which means that your measurement has a total of three significant figures, two non-zero digits and a sandwiched zero.
#color(red)(0).color(red)(0)color(purple)(1)color(darkgreen)(0)color(purple)(5) ->#three sig figs