There are 4 significant digits in 0.05730 meters.
Use the box and dot method. Draw a box around all the digits between the non-zero digits, including the nonzero digits.
Draw a box around the digits 5-7-3.
Then, if there is a decimal, box any trailing zeros. In this case there is one, so the last zero gets a box. Then count all of the boxed digits. There are four.
