# What is the easy way to find the Greatest Common Factor?

Homework HELP!!

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Mentally try to think of the largest number that will divide both numbers equally. Example: 18 and 27 The GCF is 9... nothing larger will divide either number. If you know your basic division facts well, you'll find it a breeze.

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• If you do not know your multiplication facts really well, one way is to write out the factors of each number. For instance

3/8 + 4/12

8- 8,16,24,32,40, etc...

12,- 12, 24, 36, 48, etc...

Compare the numbers they have in common

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• You can get the prime factorization and then multiply together all the prime factors that match up.

eg. 250= 2x5x5x5

40= 2x2x2x5

one 2 and one 5 match up, so the GCF is 2x5=10.

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• Have you ever done Lowest common multiple?

If you have, you can use the same method but you can only use numbers that can divide all the numbers which you are dealing with. Stop until you cannot find anymore numbers that can divide both numbers. Then you multiply the numbers you have used to divide the numbers.

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