Exercises in Manipulation
The mind's eye picture of the figures on the mental blackboard can be enlarged by practice so that the child can visualize problems of some complexity. This ability, of course, will come only after continued practice. Start with simple problems and increase their difficulty as the child progresses. You will be surprised to find how he will be able to retain the figures in his mind and soon will be able to work with them.
Write on the blackboard a column of figures as illustrated below. (A small one in the house is of great value in child training. A yard of blackboard cloth can be purchased and hung on the wall.) Allow the child to look at them for a few seconds and write down the result of his addition. Do not have him write the numbers as in previous exercises, for visualization, but only the total.
Now, add the first two numbers of the first example, subtract the third and add the fourth, then write the total.
In the second example let him add the first two, subtract the third and multiply by the fourth, write the answer.
These exercises of manipulation can be varied in many ways. The length of the columns can be accommodated to the ability of the child.