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Rounding

To reduce the number of decimal places in a number, you can round it.

$$\Tblue{2.3}45$$ rounded to one decimal place is $$\Tblue{2.3}$$

$$\Tblue{2.34}5$$ rounded to two decimal places is $$\Tblue{2.3}\Torange{5}$$.

To round a number:

  • Decide how many decimal places you want to keep.
  • Look at the digit after the last digit you want to keep.
  • If this digit is $$\le 4$$, you round down and remove everything after the digit you want to keep.
  • If this digit is $$\ge 5$$, you round up by adding one to the last digit you are keeping, and then remove everything after this.

Here are a few numbers rounded to two decimal places. The red digit is the first to be removed, it determines if we round up or down. Modified digits are in orange.

$$\Tblue{2.34}\Tred{4}6$$ $$\Tblue{3.45}\Tred{6}78$$ $$\Tblue{45.89}\Tred{9}$$ $$\Tblue{-129.09}\Tred{1}23$$ $$\Tblue{12.1}$$
$$\Tblue{2.34}$$ $$\Tblue{3.4}\Torange{6}$$ $$\Tblue{45.}\Torange{90}$$ $$\Tblue{-129.09}$$ $$\Tblue{12.1}$$