How to Round Off Decimals and Fractions
You can simplify decimals and fractions by rounding off. To round off a decimal number, you limit the number of decimal places that the number holds. To round off a fraction, you first convert the fraction to a decimal. If the division ends in a repeating decimal, you can stop after a certain number of decimal places and round off.
Rounding numbers results in an estimated or approximate value.
To round numbers:
Determine the number of places you want, and go one further.
Increase the last place you want by one number if the one further is 5 or greater.
Leave the last place you want as is, if the one further is less than 5.
Here are some examples of fractions that need to be rounded:
Example 1: The fraction 5/9 won't divide evenly — it ends in a repeating decimal.
Change 5/9 to a decimal by dividing 5 by 9.
5 ÷ 9 = .5555
If you choose to round to three decimal places, look one digit beyond the third decimal place, which is 5.
If the digit is 5 or greater, then you round up.
So .5555 ≈ .556
The symbol ≈ means approximately the same or about equal. This is a useful symbol for when you are rounding a number.
Example 2: The fraction 4/7 won't divide evenly — it’s another repeating decimal that'll go on forever when divided.
Change 4/7 to a decimal by dividing 4 by 7.
4 ÷ 7 = .57142857142857
If you choose to round to 4 decimal places, look at the first digit beyond the fourth decimal place, which is 2.
If the digit is less than 5, then you don't round up.
So .57142 ≈ .5714