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LCM of 18 and 30

The least common multiple (LCM) of 18 and 30 is 90. Their greatest common factor (GCF) is 6.

LCM90
GCF6
Prime factors of 182 × 3^2
Prime factors of 302 × 3 × 5

Prime factorization method

Write each number as a product of primes: 18 = 2 × 3^2 and 30 = 2 × 3 × 5. The LCM takes every prime with its highest power, which gives 90. The GCF takes only the shared primes with their lowest power, which gives 6.

Check with the formula

For two numbers, LCM × GCF = a × b. Here 90 × 6 = 540, and 18 × 30 = 540, so the answer is correct.

Multiples of 18 and 30

Multiples of 18: 18, 36, 54, 72, 90, 108, 126, 144 … Multiples of 30: 30, 60, 90, 120, 150, 180, 210, 240 … The first number that appears in both lists is 90.

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Frequently asked questions

What is the LCM of 18 and 30?

The LCM of 18 and 30 is 90. It is the smallest positive number that both 18 and 30 divide into exactly.

What is the GCF of 18 and 30?

The greatest common factor of 18 and 30 is 6. It is the largest number that divides both without a remainder.

How do I find the LCM of 18 and 30 quickly?

Divide the product by the GCF: 18 × 30 = 540, and 540 ÷ 6 = 90.