Calculate the Greatest Common Factor or GCF of 180, 378 and 420
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The instructions to find the GCF of 180, 378 and 420 are the next:
1. Decompose all numbers into prime factors
| 180 | 2 |
| 90 | 2 |
| 45 | 3 |
| 15 | 3 |
| 5 | 5 |
| 1 |
| 378 | 2 |
| 189 | 3 |
| 63 | 3 |
| 21 | 3 |
| 7 | 7 |
| 1 |
| 420 | 2 |
| 210 | 2 |
| 105 | 3 |
| 35 | 5 |
| 7 | 7 |
| 1 |
2. Write all numbers as the product of its prime factors
| Prime factors of 180 | = | 22 . 32 . 5 |
| Prime factors of 378 | = | 2 . 33 . 7 |
| Prime factors of 420 | = | 22 . 3 . 5 . 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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