Calculate the Greatest Common Factor or GCF of 21
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The instructions to find the GCF of 21 are the next:
1. Decompose all numbers into prime factors
| 21 | 3 |
| 7 | 7 |
| 1 |
2. Write all numbers as the product of its prime factors
| Prime factors of 21 | = | 3 . 7 |
3. Choose the common prime factors with the lowest exponent
Common prime factors: 3 , 7
Common prime factors with the lowest exponent: 31, 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 = 31. 71 = 21
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