Significant figures are the digits which play a role in defining a measurement that is they carry some meaning.
There are <em>three</em> essential rules to find out the significant figures in a given number:
<u>Rule 1</u>: Non-zero digits such are always significant.
<u>Rule 2</u>: The zeroes after a non-zero number in decimal are also significant. An example is if the number is 0.0500 then the zeroes after 5 are considered significant, however, the zeroes before 5 are not significant.
<u>Rule 3:</u> The zeroes placed between any two significant digits are also considered as significant e.g in 202 the zero is significant.
Therefore, in the number 0.020 km, there are <em>two</em> significant digits, one is 2 and the other is the last zero placed after 2.
