Significant figures give an idea of the accuracy of a number. Imagine having two tape measures, one with markings every decimetre
and the other with the millimetres marked. The second can make a more accurate measurement than the first. We can use significant figures to show the difference.
The first might report the length of this pool at 25.0 metres, meaning that the length is closest to the marking 25.0 metres on the measuring tape.
The second is much more accurate so might come up with a length of 25.008 metres, meaning that it finds the length to be closest to the 25.008 metres mark on the measuring tape.
Placeholders, or digits that have not been measured, are
not considered significant. For example, in a measurement of 0.0123
L the leading two `0`s are
placeholders and therefore are not significant. All other digits are
If a decimal number starts with a string of "0" we call these "0"s the leading "0"s and if it ends with a string of "0" we call them trailing "0"s.
Rules for significant figures: