Calculate the Greatest Common Factor or GCF of 18, 28 and 40
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The instructions to find the GCF of 18, 28 and 40 are the next:
1. Decompose all numbers into prime factors
| 18 | 2 |
| 9 | 3 |
| 3 | 3 |
| 1 |
| 28 | 2 |
| 14 | 2 |
| 7 | 7 |
| 1 |
| 40 | 2 |
| 20 | 2 |
| 10 | 2 |
| 5 | 5 |
| 1 |
2. Write all numbers as the product of its prime factors
| Prime factors of 18 | = | 2 . 32 |
| Prime factors of 28 | = | 22 . 7 |
| Prime factors of 40 | = | 23 . 5 |
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
Also calculates the: