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GCF/LCM

Greatest Common Factor

Factors are the numbers that are multiplied to get an answer.

First: List the factors for each number given.

Second: Cross out all factors that are not common among all numbers.

Third: Circle the biggest factor that all numbers share.

Example:

18                                                                          24

1 X 18                                                                1 X 24

2 X 9                                                                  2 X 12

3 X 6                                                                  3 X 8

                                                                            4 X 6

1,2,3,6,9,18                                               1,2,3,4,6,8,12,24

Common Factors: 1,2,3,6

Greatest Common Factor: 6

 

Least Common Multiple

Multiples are the products that you get when you multiply a number. 

For example: The multiples of 3 are: 3, 6, 9, 12, 15, 18, 21, 24....

To find the least common multiple for given numbers:

First: List the multiples for each number given

Then: Find the first number that they both share.

Example:

4: 4, 8, 12, 16, 20, 24, 28, 32

5: 5, 10, 15, 20, 25, 30, 35

The least common multiple for 4 & 5 is 20.

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