Procedure

  1. Ignore the decimal marks - they are not important until you reach step three.

  2. Multiply the two figures.

  3. Count the number of decimal places of both coefficients and add them up. In this case, each figure has one decimal place. Take the result of your multiplication and place a decimal mark in a way that the result receives as many decimal places as both coefficients combined ( 2 in this example.)

%%2.5 \cdot 1.1 \rightarrow 25\cdot11%%

%%\begin{array}{l}\underline{25\cdot11}\\ \hphantom{000}25\\ \underline{\hphantom{26}250}\\ \hphantom{20}275 \end{array}%%

%%\hphantom{2,}2.75%%

Special Cases

While multiplying decimal fractions, watch out for the following special cases:

  • If the result of your multiplication contains any zeros at the end of the figure, remember that these need to be taken into account when placing the decimal mark. After adding the decimal mark, they can be ommited as usual.

  • Another special case is the multiplication with %%10,100,1000,…%%. The decimal mark is simply shifted to the right by as many places as there are zeros in the coefficient. Example: %%3.4 \cdot 100=34\cdot 10=340%%

  • Similar to the case detailed above, multiplying with %%0.1; 0.1; 0.01 ;…%% shifts the decimal mark to the left by one place per zero in the coefficient. Do not forget the zero in front of the decimal mark! Example: %%3.4\cdot 0.01=0.34\cdot 0.1=0.34%%

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