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Greatest Common Factor

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Greatest Common Factor

Calculate the Greatest Common Factor or GCF of 28, 58, 78 and 88

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The instructions to find the GCF of 28, 58, 78 and 88 are the next:

1. Decompose all numbers into prime factors

28	2
14	2
7	7
1

58	2
29	29
1

78	2
39	3
13	13
1

88	2
44	2
22	2
11	11
1

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

Prime factors of 28	=	2² . 7
Prime factors of 58	=	2 . 29
Prime factors of 78	=	2 . 3 . 13
Prime factors of 88	=	2³ . 11

3. Choose the common prime factors with the lowest exponent

Common prime factors: 2

Common prime factors with the lowest exponent: 2¹

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 = 2

Also calculates the:

Least Common Multiple or LCM of 28, 58, 78 and 88

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