Calculate the Greatest Common Factor or GCF of 13, 18, 21 and 28
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The instructions to find the GCF of 13, 18, 21 and 28 are the next:
1. Decompose all numbers into prime factors
| 13 | 13 |
| 1 |
| 18 | 2 |
| 9 | 3 |
| 3 | 3 |
| 1 |
| 21 | 3 |
| 7 | 7 |
| 1 |
| 28 | 2 |
| 14 | 2 |
| 7 | 7 |
| 1 |
2. Write all numbers as the product of its prime factors
| Prime factors of 13 | = | 13 |
| Prime factors of 18 | = | 2 . 32 |
| Prime factors of 21 | = | 3 . 7 |
| Prime factors of 28 | = | 22 . 7 |
3. Choose the common prime factors with the lowest exponent
Common prime factors: None
Common prime factors with the lowest exponent: None
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.
Since there are not common prime factors the GCF is 1
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