Chapter 11 The Study Of Numbers Up To 1000—Ii

8 × 67 = 67 × 2 × 2 × 2 = 134 × 2 × 2 = 268 × 2 = 536 This method can also be applied to multiplications by 16, 32 and 64. Again, in order not to restrict the pupil’s ability to a single technique, he should become acquainted with the alternative methods of multiplying by 4 and by 8: 4 × 73 = 4 × 70 + 4 × 3 = 280 + 12 = 292 8 × 67 = 8 × 60 + 8 × 7 = 480 + 56 = 536

Multiplying By 20, 40, 80 And By 50 Mastery having been obtained over doubling and over multiplications by 10, 2, 4, 8 and 5, it becomes a comparatively simple step to understand multiplications by 20, 40, 80 and by 50, making use of the corresponding ‘threes’ and ‘fours’. Thus: 17 × 20 = 17 × 10 × 2 = 170 × 2 = 340 = 17 × 2 × 10 = 34 × 10 = 340 17 × 40 = 17 × 10 × 2 × 2 = 170 × 2 × 2 = 340 × 2 = 680 = 17 × 2 × 2 × 10 = 34 × 2 × 10 = 68 × 10 = 680 17 × 80 = 17 × 10 × 2 × 2 × 2 = 170 × 2 × 2 × 2 = 340 × 2 × 2 = 680 × 2 = 1360 = 17 × 2 × 2 × 2 × 10 = 34 × 2 × 2 × 10 = 682 × 2 × 10 = 136 × 10 = 1360

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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

The Cuisenaire Gattegno method of teaching Mathematics