Calculate the Greatest Common Factor or GCF of 20, 30, 66 and 130
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The instructions to find the GCF of 20, 30, 66 and 130 are the next:
1. Decompose all numbers into prime factors
| 20 | 2 |
| 10 | 2 |
| 5 | 5 |
| 1 |
| 30 | 2 |
| 15 | 3 |
| 5 | 5 |
| 1 |
| 66 | 2 |
| 33 | 3 |
| 11 | 11 |
| 1 |
| 130 | 2 |
| 65 | 5 |
| 13 | 13 |
| 1 |
2. Write all numbers as the product of its prime factors
| Prime factors of 20 | = | 22 . 5 |
| Prime factors of 30 | = | 2 . 3 . 5 |
| Prime factors of 66 | = | 2 . 3 . 11 |
| Prime factors of 130 | = | 2 . 5 . 13 |
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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