# Rounding to significant figures

The method of rounding to a significant figure is often used as it can be applied to any kind of number, regardless of how big or small it is. When a newspaper reports a lottery winner has won £3 million, this has been rounded to one significant figure. It rounds to the most important figure in the number.

To round to a significant figure:

1. look at the first non-zero digit if rounding to one significant figure
2. look at the digit after the first non-zero digit if rounding to two significant figures
3. draw a vertical line after the place value digit that is required
4. look at the next digit
5. if the next digit is 5 or more, increase the previous digit by one
6. if it is 4 or less, keep the previous digit the same
7. fill any spaces to the right of the line with zeros, stopping at the decimal point if there is one

### Examples

Round 53,879 to 1 significant figure, then 2 significant figures.

• 5|3879 to 1 significant figure is 50,000
• 53|879 to 2 significant figures is 54,000

Notice that the number of significant figures in the question is the maximum number of non-zero digits in your answer.

Round 0.005089 to 1 significant figures, then 2 significant figures.

• 0.005|089 to 1 significant figure is 0.005
• 0.0050|89 to 2 significant figures is 0.0051
Question

What is 98,347 rounded to 1 significant figure, and 2 significant figures?

• 9|8347 to 1 significant figure is 100,000
• 98|347 to 2 significant figures is 98,000
Question

What is 3.5175 rounded to 1 significant figure, and 2 significant figures?

• 3|.5175 to 1 significant figure is 4
• 3.5|175 to 2 significant figures is 3.5