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Factors
Factors are the numbers you multiply together to get another number.
When you find the factors of a number you list the multiplication facts that equal that number.
Example: Find the Factors of 12: 1 x 12, 2 x 6, 3 x 4
Therefore, the factors of 12 are 1,2,3,4,6,12.
What is a "Common Factor" ?
Let us say you have worked out the factors of two or more numbers:
Example:
The factors of 12 are 1, 2, 3, 4, 6 and 12
The factors of 30 are 1, 2, 3, 5, 6, 10, 15 and 30
Then the common factors are those that are found in both numbers:
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Notice that 1,2,3 and 6 appear in both lists?
So, the common factors of 12 and 30 are: 1, 2, 3 and 6
Try It:
List the factors of each number and then circle the ones they have in common.
18
24
The Greatest Common Factor or GCF is the greatest number they have in common.
Look at the factors of 12 and 30 what is the GCF?_______
Look at the factors of 18 and 24 what is the GCF?_______
Prime Number- a numbers whose factors are only 1 and itself.
Composite Number- has factors other than just 1 and itself.
Multiples
The multiples of a number are what you get when you multiply it by other numbers
(such as if you multiply it by 1,2,3,4,5, etc).
Here are some examples:
The multiples of 3 are: 3, 6, 9, 12, 15, 18, 21, etc ...
The multiples of 12 are: 12, 24, 36, 48, 60, 72, etc...
What is a "Common Multiple" ?
When you list the multiples of two (or more) numbers, and find the same value in both
lists, then that is a common multiple of those numbers.
For example, when you write down the multiples of 4 and 5, the common multiples are
those that are found in both lists:
The multiples of 4 are: 4,8,12,16,20,24,28,32,36,40,44,...
The multiples of 5 are: 5,10,15,20,25,30,35,40,45,50,...
The Least Common Multiple is the first number they have in common. What
is the LCM of 4 and 5? ___________
Try It: List the first 8 multiples of each number and circle the LCM.
7
3