Calculate the Greatest Common Factor or GCF of 28, 42 and 54
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The instructions to find the GCF of 28, 42 and 54 are the next:
1. Decompose all numbers into prime factors
| 28 | 2 |
| 14 | 2 |
| 7 | 7 |
| 1 |
| 42 | 2 |
| 21 | 3 |
| 7 | 7 |
| 1 |
| 54 | 2 |
| 27 | 3 |
| 9 | 3 |
| 3 | 3 |
| 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 54 | = | 2 . 33 |
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
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