The dynamic model for subtracting two 2-digit numbers

Base ten system and its respective materials provide an effective dynamic model for addition that allow children to recognize the importance of adding ones to ones, tens to tens and so on. This model also is used to demonstrate the processes involved in regrouping. In the case of subtraction: when it is not possible to remove some ones from some ones, or some tens from some tens, or some hundreds from some hundreds etc. then exchange 1 ten for 10 ones and add to some ones, exchange 1 hundred for 10 tens and add to some tens, exchange 1 thousand for 10 hundreds and add to some hundreds etc., if necessary, in order to perform the subtraction of the digits. The use of such models is so important: they help children understand the procedures involved in addition and subtraction algorithms. Here is the geometrical representation of the addition operation (Dynamic Model) for 43 - 16 .