Calculate the Greatest Common Factor or GCF of 20, 36, 126 and 128
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The instructions to find the GCF of 20, 36, 126 and 128 are the next:
1. Decompose all numbers into prime factors
| 20 | 2 |
| 10 | 2 |
| 5 | 5 |
| 1 |
| 36 | 2 |
| 18 | 2 |
| 9 | 3 |
| 3 | 3 |
| 1 |
| 126 | 2 |
| 63 | 3 |
| 21 | 3 |
| 7 | 7 |
| 1 |
| 128 | 2 |
| 64 | 2 |
| 32 | 2 |
| 16 | 2 |
| 8 | 2 |
| 4 | 2 |
| 2 | 2 |
| 1 |
2. Write all numbers as the product of its prime factors
| Prime factors of 20 | = | 22 . 5 |
| Prime factors of 36 | = | 22 . 32 |
| Prime factors of 126 | = | 2 . 32 . 7 |
| Prime factors of 128 | = | 27 |
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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