If you want to add up or subtract decimal fractions you can use the same techniques used to add up or subtract integers.

You only need to pay attention to the position of the decimal mark.

Addition of decimal fractions

There are multiple methods to add up decimal fractions. You can either

  • write the figures underneath each other and use written addition,
  • or convert them into regular fractions and add them up this way.

Procedure

$$6.256+2.73\\$$

Write the figures underneath each other so that the decimal marks are directly beneath each other. If the figures contain a different amount of decimal places you need to fill up the shorter number with zeros until they both have the same number of decimal places.

%%\begin{array}{l} \hphantom{ +\; } 6.256\\ +\;2.730\\ \\ \end{array}%%

Add up the numbers without paying attention to the decimal marks. Then place the decimal mark of the solution directly underneath the others.

%%\begin{array}{l} \hphantom{ +\; } 6.256\\ \underline{+\;2.730}\\ \hphantom{ +\; }8.986 \end{array}%%

Subtraction of decimal fractions

As with the addition of decimal fractions, there are two different approaches you can use. You can either

  • write them underneath each other and use written subtraction
  • or convert them to regular fractions and subtract them.

Procedure

%%6.623-4.71\\%%

Write the figures underneath each other so that the decimal marks are directly beneath each other. If the figures contain a different amount of decimal places you need to fill up the shorter number with zeros until they both have the same number of decimal places.

%%\begin{array}{l} \hphantom{ -\; } 6.623\\ -\;4.710\\ \\ \end{array}%%

Use written subtraction without paying attention to the decimal marks. Then place the decimal mark of the solution directly underneath the others.

%%\begin{array}{l} \hphantom{ -\; } \overset{5}{\not6}.\overset{16}{\not6}\;2\;3\\ \underline{-\;\;4.\;7\;1\;0}\\ \hphantom{-\;}\;1.\;9\;1\;3 \\ \end{array}%%

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