INTRODUCTION :  When a child of seven isn't able to solve the sum 23+9, what could the reasons be? When she is asked to subtract 9 from 16, why does she write 9 - 16 =13 ? It could be because she hasn't understood one or more of the concepts / skills involved in the process of addition.

These are the ability to count, familiarity with numbers and numerals upto 100, an understanding of place value, the concept of addition and the ability to apply the addition algorithm with understanding. In Units 5 and 6 we have seen some ways of helping the child to deal with problems related to number, numerals, counting and place value. In this unit we concentrate on looking at ways of conveying the meaning and algorithms of addition and subtraction to children.

We start the unit with a discussion on ways of developing an understanding of addition. Then we do the same in the context of subtraction. We stress the fact that these operations must be introduced to children using concrete objects to start with. They must be exposed lo related word problems from the early stages on. And these operations should be introduced to them more or less together.

Following this, we have discussed reasons for errors children make while mechanically applying the algorithms. What comes out in this discussion is that, unfortunately, we usually tend to identify addition or subtraction with the algorithm for doing them. We ignore the fact that addition or subtraction involves an understanding of class inclusion, of units of objects and the algorithms. All these aspects need to be understood by a child before she can be said to 'know' these operations. Here we have talked of some ways of remedying the situation.

And, finally, we have considered the importance of developing the child's ability to estimate computed sums or differences of numbers. Following this, we have looked at some activities that help children develop this skill.

Throughout the unit we look at certain misconceptions that children are likely to form while addition or subtraction are taught in the classroom. Why they may have come about and strategies for helping children to get rid of them have been talked about. Of course, as always, we have suggested an activity-based learner-oriented approach in teaching the concepts.