Calculate the Greatest Common Factor or GCF of 20 and 30
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The instructions to find the GCF of 20 and 30 are the next:
1. Decompose all numbers into prime factors
| 20 | 2 |
| 10 | 2 |
| 5 | 5 |
| 1 |
| 30 | 2 |
| 15 | 3 |
| 5 | 5 |
| 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 |
3. Choose the common prime factors with the lowest exponent
Common prime factors: 2 , 5
Common prime factors with the lowest exponent: 21, 51
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. 51 = 10
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