Finding the Greatest Common Factor

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Finding the Greatest Common Factor
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The greatest common factor of two or more numbers
is the greatest number that is a factor of every
number.
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There are two methods for finding the
GCF.1. Listing the factors2. Using the
Ladder
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To find the GCF of two numbers using a list, list
the factors of one number. Then list the factors
of the second number. The GCF is the greatest
value that appears on both lists.
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1. Make a list to find the GCF of 18 and 3018
1, 2, 3, 6, 9, 1830 1, 2, 3, 5, 6, 10, 15, 30
THE GCF of 18 and 30 is 6.
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To find the GCF of two numbers using the ladder
method, determine a prime number that you can
divide evenly into each number. Write the number
on the side and divide. Continue as far as you
can!
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27 36
2. Use a ladder to find the GCF of 27 and 36
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3 x 3 9 so the GCF is 9
9 12
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3 4