Calculate the Greatest Common Factor or GCF of 15, 45 and 90
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The instructions to find the GCF of 15, 45 and 90 are the next:
1. Decompose all numbers into prime factors
| 15 | 3 |
| 5 | 5 |
| 1 |
| 45 | 3 |
| 15 | 3 |
| 5 | 5 |
| 1 |
| 90 | 2 |
| 45 | 3 |
| 15 | 3 |
| 5 | 5 |
| 1 |
2. Write all numbers as the product of its prime factors
| Prime factors of 15 | = | 3 . 5 |
| Prime factors of 45 | = | 32 . 5 |
| Prime factors of 90 | = | 2 . 32 . 5 |
3. Choose the common prime factors with the lowest exponent
Common prime factors: 3 , 5
Common prime factors with the lowest exponent: 31, 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 = 31. 51 = 15
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