Chapter 12 Discovering Systematic Procedures

The operation could be made purely mechanical in the following way: Note that 6 + 4 = 10 while 8 + 1 = 7 + 2 = 5 + 4 = 6 + 3 = 9, so that the complement of the number to be subtracted to the nearest power of 10 only requires the knowledge of the complements in 10 and in 9. This then leads to the easiest of all transformations. Pupils are then challenged to write down any subtraction, changing it to one in which the second term becomes the appropriate power of ten, always remembering that they must keep to an equivalent difference. 6 Checking answers Pupils should be reminded of their earlier experiences concerning the relation between addition and subtraction. Knowing that if 7 – 3 = 4 then 4 + 3 = 7, they can check every subtraction by adding their answer to the number in the second term. For example:

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The Cuisenaire Gattegno method of teaching Mathematics
The Cuisenaire Gattegno method of teaching Mathematics

The Cuisenaire Gattegno method of teaching Mathematics