RELATING ADDITION AND SUBTRACTION : In the earlier sections we have stressed the fact that to help children understand addition or subtraction, they need to be exposed to various situations which require them to add or subtract. Regarding this matter, we spoke to some people who are involved in studying ways in which children learn mathematical concepts. In response to this, one of them told us how he communicated addition and subtraction. What he had to say is given in the example below.
Example: Raza has been trying out different teaching strategies in a primary school for some years. According to him, children should first be made to add small numbers of toys food items, objects found around them, and so on. After enough exposure of this kind, they could be helped to develop a sense of subtraction (by methods suggested in.Sec.7.3). And while they are learning subtraction the relationship between the two operations should be brought out.
He finds that with enough experience of adding familiar objects, they would learn that, say, 3 marbles and 2 marbles are 5 marbles. With similar exposure, they would realise how much is left if you take away 3 marbles from 5 marbles. Then he helps them to relate the two operations, by first giving them, say, 3 laddus and 2 laddus and asking how many laddus they have. After this he asks them to take away 2 laddus from the 5 they have (hopefully, they haven't eaten any up!) and say how many are left. He does this kind of activity with a variety of objects - toffees, spoons, balls, and so on In this way the children learn to understand 'take away', and relate it to 'add'.
Once children have practised both these concepts in the contest of small quantities of objects, he moves them to the pictorial stage. At the same time he introduces them to the symbol '+'. After some practise with such pictures and the symbolic representation, he does the same with subtraction. For this operation, he shows them a 3 +4=7 picture like that in Fig. 5(a), and asks them first, "How many are there?'Then, in front of them he strikes out, say, two (see Fig.5 (b)), and says, "If I take away two, how many are the same time, below that he writes down 5-2 = 3 .