  # Rounding to 1, 2 or 3 Significant Figures

In this worksheet, students practise rounding to 1, 2 or 3 significant figures. Key stage:  KS 3

Curriculum topic:   Number

Curriculum subtopic:   Round/Approximate Numbers Appropriately

Difficulty level:   #### Worksheet Overview

Significant means important.

1 significant figure

In the number 4725, the number 4 is the most significant. It has the value 4000.

But 4725 is closer to 5000 than 4000.

Following the normal rules of rounding, 4725 becomes 5000 when rounded to 1 significant figure. Rounding to 1 significant figure is the least accurate way of rounding.

2 significant figures

Rounding to 2 significant figures is more accurate. We now look at the second number, and round accordingly.

4725 is closer to 4700 than 4800.

4725 is 4700 to 2 sig. figs.

3 significant figures

Rounding to 3 significant figures, we look at the third digit.

4725 is "closer" to 4730 than to 4720. (Remember 5 rounds up)

4725 rounds to 4730 to 3 sig. figs.

Common mistake

It is a common mistake to say that 4725 rounds to 5 to 1 sig. fig., instead of 5000.

The zeros here are important to get the place values correct. They are important but not significant.

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