Approximation - Significant figures - decimals

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.

Counting 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:

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