Åk 6–9
 
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4.2 Rules of Rounding
What we do when we round is to look at the digit that follows the decimal that we want to round off by.

If the following digit is a 0, 1, 2, 3 or 4, we round down.

If the following digit is a 5, 6, 7, 8, or 9 we round up.


Here are a few examples which you will encounter:

1. Round 3.273 to two decimals (hundredths)
We then look at the digit after the 7 and see that it is a 3: 3.273.  We then round the number to 3.27

2. Round 9.45 to one decimal (tenths)
Here we look at the digit after the 4 and see that it is a 5: 9.45. We then round the number to 9.5.

3. Round 243.5719 to three decimals (thousandths)
Here we look at the fourth decimal (the one after the 1) and see that it is a 9: 243.5719.  The number is rounded to 243.572.

4. Round 2.3791 to one decimal (tenths)
Here we look at the second decimal and see that it is a 7: 2.3791.  The number is then rounded to 2.4.