Rounding 12.756 or 4.543 to 1 decimal place (d.p.) seems sensible, as the rounded figures are very close to the actual value.
12.756 = 12.8 (1 d.p.)
4.543 = 4.5 (1 d.p.)
But what happens if you round a very small number to 1 d.p?
0.00546 = 0.0 (1 d.p.)
0.00213 = 0.0 (1 d.p.)
This is not a useful answer. Another way to find an approximate answer with very small numbers is to use significant figures.
Significant figures start at the first non-zero number, so ignore the zeros at the front, but not the ones in between. Look at the following examples:
From the first significant figure onwards, all zeros are included. It's only the zeros at the beginning that don't count.
How many significant figures do the following numbers have?
a) 0.3007 has four significant figures.
b) 2.01 has three significant figures.
c) 0.001023 has four significant figures.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.