Chapter 7 The Study Of Numbers Up To 20

Numbers that have factors are called composite numbers. Those that have no factors, other than 1 and themselves, are called prime numbers. Write down a few composite numbers that you know (or have found). Write down all the prime numbers up to 20. Here is how some composite numbers are formed: 6 = 2 × 3 and 3 × 2 4=2×2 12 = 4 × 3, 3 × 4, 2 × 6 and 6 × 2. Show how these composite numbers can be formed: 15 =

18 =

9=

Discovering remainders in short division Make a mat for 13, trying to use rods of one color only, and then complete the length with the appropriate rod. The mat can first be read as multiplications, for e× ample, 13 = 2 × 5 + 3. The pupils can then be asked: ‘How many 2’s in 13?’ (6, but one must be added, or, 6 with one left over). ‘How many 4’s in 13? 6’s in 13?’ and so on.

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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