Factors and Prime Numbers

Material

• Peg board; a wooden board perforated with 900 holes used for factoring, squaring, and square roots.
• Box of coloured pegs.

Presentation

1. Give the child slips with a number on each between 1 and 100.
2. The child takes the number of pegs, e.g. 15, and sees how many complete lines he can make, beginning with 2. ‘This is no good, there is 1 over’; then lines of 3 ‘yes 5 complete rows!’

4-no.

5-yes: 3 complete rows

6-no

7-no

etc.

When he finds what numbers will go exactly he fills up 2 charts.

Chart A     Giving the numbers and factors, e.g.2=2×1

   3=3×1
   4=2×2
   5=5×1
   6=6×1
       3×2

       2×3

Chart B           

Numbers 1 to 100. Put circle round each when it is a factor. Some numbers have no circles.They are PRIME NUMBERS.