# Understanding Significant Figures

A specific number of significant figures can also be used to approximate numbers (s.f.). The most significant figure in the number 54.36 is 5, which has a value of 50. The 6 is the least significant, as it only carries a value of 6 hundredths of a percent.

**Examples:
**

a) Write 43.26 to 3 s.f.

Only the three most significant digits are written; however, the fourth digit must be taken into account when determining whether or not the third digit should be rounded up.

43.26, for example, is expressed as **43.3** to 3 s.f.

b) Write 0.0042 to 1 s.f.

Only two digits, the 4 and the 2, are significant in this scenario. Because the 4 is the more important of the two, it is the only one to be written in the solution.

0.0042, for example, is expressed as **0.004** to 1 s.f.

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