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Multiple
A multiple is a number that is the product of a Highest Common Factor (HCF)
given number and some other number.
The biggest number that is the factor of each
number.
6x3 = 13
\ 12:1,2, 3, 4, 6,12 These are the factor
multiple 9:1,3,9
lists of 12 and 9
Factor
HCF = 3
A factor is a number that is multiplied with
another number to get a product. Lowest Common Multiple (LCM)

The smallest number that is a common
6x 3 = 13
multiple of two or more numbers.
factor 6 and 8
1x6=6 1x8=8
Prime numbers
2x6 = 12 2x8 = 16
Prime numbers are numbers which have only
3X6 = 18 3X8 = 24
two factors: 1 and the number itself. The
4 X 6 = 24
prime numbers below 100 are:
CO
LCM = 24

1 2 3 4 5 6 7 8 9 10 Factor tree
11 12 13 14 15 16 17 18 19 20 A factor tree can be used to find HCFs and
LCMs.
21 22 23 24 25 26 27 28 29 30
This is an example of a factor tree for the
31 32 33 34 35 36 37 38 39 40 number 24:
41 42 43 44 45 46 47 48 49 50

51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 69 70
71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90
91 92 93 94 95 96 97 98 99 100

Sieve of Eratosthenes
So, 24 = 2 x2 x2 x3
The sieve of Eratosthenes is a method of
finding prime numbers. The result is a
hundred grid as shown above.

UNIT 1 I Factors, Multiples and Primes