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.
10
12
9
16
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15
10
14
7
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