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Calculate the Greatest Common Factor or GCF of 28, 42, 56 and 98

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The instructions to find the GCF of 28, 42, 56 and 98 are the next:

1. Decompose all numbers into prime factors

282
142
77
1
422
213
77
1
562
282
142
77
1
982
497
77
1

2. Write all numbers as the product of its prime factors

Prime factors of 28=22 . 7
Prime factors of 42=2 . 3 . 7
Prime factors of 56=23 . 7
Prime factors of 98=2 . 72

3. Choose the common prime factors with the lowest exponent

Common prime factors: 2 , 7

Common prime factors with the lowest exponent: 21, 71

4. Calculate the Greatest Common Factor or GCF

Remember, to find the GCF of several numbers you must multiply the common prime factors with the lowest exponent.

GCF = 21. 71 = 14


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