What are the common factors of 12 and 18 and what is their highest common factor? What is their lowest common multiple?

The factors of 12 are 1, 2, 3, 4, 6, and 12. The factors of 18 are 1, 2, 3, 6, 9, and 18.

The common factors of 12 and 18 are the numbers which appear in both lists of factors: 1, 2, 3, and 6. The highest common factor is the largest of these, 6.

For the lowest common multiple, we divide the two numbers by their highest common factor: 12/6 = 2 and 18/6 = 3. Then the lowest common multiple is found by multplying these three numbers: 6 × 2 × 3 = 36.

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Last updated: 3 October, 2007.