PRIME NUMBERS

2 3 5 7 11 13 17 19 23 29

WHAT ARE FACTORS?

NUMBERS THAT DIVIDE INTO OTHER NUMBERS EXACTLY

WHAT ARE PRIME FACTORS?

FACTORS THAT ARE PRIME NUMBERS

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

IS 30 AN EVEN NUMBER?

YES

DIVIDE IT BY 2

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

30 215

THE FIRST PRIME FACTOR

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

IS 15 AN EVEN NUMBER?

NO

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

IS 15 A PRIME NUMBER?

NO

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

WILL 15

DIVIDE

BY 3?

YES

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

30 21535

THE SECOND PRIME FACTOR

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

IS 5 AN EVEN NUMBER?

NO

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

IS 5 A PRIME NUMBER?

YES

ALL THE PRIME FACTORS HAVE BEEN FOUND

WRITE 30 AS A PRODUCT OF ITS PRIME FACTORS

30 = 2 x 3 x 5

WRITE 180 AS A PRODUCT OF ITS PRIME FACTORS

180 2

90

45

15

5

2

3

3

180 = 2 x 2 x 3 x 3 x 5PRACTICE

Greatest

COMMON

FACTOR

FIND THE GCF OF 120 AND 180

1. Find the prime factors of each number

120 = 2 x 2 x 2 x 3 x 5

180 = 2 x 2 x 3 x 3 x 5

2. Find the prime factors that are common

HCF = 2 x 2x 3 x 5 3. Work out the GCF

= 60

PRACTICE

Least

COMMON

MULTIPLE

FIND THE LCM OF 36 AND 56

1. Find the prime factors of each number

36 = 2 x 2 x 3 x 3

56 = 2 x 2 x 2 x 7 2. Write down the first set of factors again

2 x 2 x 3 x 3

3. Check each factor of the second set is in the LCM – if not add them

2 and 7 are

missing

x 2 x 7

2 and 7 are

missing

LCM = 504

PRACTICE