Calculate the Greatest Common Factor or GCF of 42, 66, 78 and 126
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The instructions to find the GCF of 42, 66, 78 and 126 are the next:
1. Decompose all numbers into prime factors
42 | 2 |
21 | 3 |
7 | 7 |
1 |
66 | 2 |
33 | 3 |
11 | 11 |
1 |
78 | 2 |
39 | 3 |
13 | 13 |
1 |
126 | 2 |
63 | 3 |
21 | 3 |
7 | 7 |
1 |
2. Write all numbers as the product of its prime factors
Prime factors of 42 | = | 2 . 3 . 7 |
Prime factors of 66 | = | 2 . 3 . 11 |
Prime factors of 78 | = | 2 . 3 . 13 |
Prime factors of 126 | = | 2 . 32 . 7 |
3. Choose the common prime factors with the lowest exponent
Common prime factors: 2 , 3
Common prime factors with the lowest exponent: 21, 31
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. 31 = 6
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