Rounding decimals

## Rounding using rules

We can round numbers using conventions or rules for rounding. We refer to the digit to be considered as the **rounding digit**. For example, if the number 3.168 is to be rounded to 2 decimal places then 6 is the rounding digit.

- If the digit following the rounding digit is 0, 1, 2, 3 or 4 the rounding digit stays the same.
- If the digit following the rounding digit is 5, 6, 7, 8 or 9 the rounding digit will increase by 1.

When the rounding is completed, the digits following the rounding digit are discarded.

Following this convention 3.168 is 3.17 when rounded correct to 2 decimal places.

## Illustrating rounding using a number line

#### Question 1

Round 6.72 correct to 1 decimal place (tenths).

#### Solution

- 7 is the rounding digit.
- 6.72 lies between 6.70 and 6.80.
- 2 is less than 5.
- Therefore we round it down to 6.7.

As shown on the number line, 6.72 is closer to 6.70 than to 6.80. |

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