Prime Factors

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Monday, 19 October 2009
Prime Factors
Objective Write a number as a product of its
prime factors. Find the HCF and LCM of two numbers
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Prime Numbers A prime number is a number that can
only be divided (exactly) by itself and 1.
12 2 6 12 3 4 12 6 2
12 can be divided by 2, 4 and 6 so 12 is not a
prime number.
7 7 1 7 1 7
7 can only be divided by itself and 1 to give an
integer answer. 7 is a prime number
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Write down the prime numbers between 1 and 40.
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Factors Factors are the numbers that multiply
together to give a certain number. The factor
pairs of 12 are 1 x 12 12 2 x 6 12 3 x 4
12 4 x 3 12 6 x 2 12 12 x 1 12
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The prime factors of 12 are 2 x 2 x 3 12
Prime numbers
12
6
2
3
2
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Find the Highest Common Factor (HCF) of 36 and 72
1. Find the prime factors of both numbers 36 2
x 2 x 3 x 3 72 2 x 2 x 2 x 3 x 3 2. Use
one of each of the numbers that are in both lists
HCF 2 x 2 x 3 x 3 HCF
36
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Find the Lowest Common Multiple (LCM) of 36 and 90
1. Find the prime factors of both numbers 36 2
x 2 x 3 x 3 90 2 x 3 x 3 x 5 2. Use one of
each of the numbers that are in both lists and
all the remaining numbers. LCM
2 x 3 x 3 x 2 x 5 LCM 180
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1. Find the HCF of 12 and 30. 2. Find the HCF of
54 and 180. 3. Find the LCM of 18 and 30. 4. Find
the LCM of 24 and 84. 5. Find the LCM of 54 and
120 6. Find the LCM of 72 and 150
1. 6 2. 18 3. 90 4. 168