GCF and LCM

The LCM of two or more numbers is the smallest multiple that is exactly divisible by each of the numbers.

List the multiples of each number: 2: 2, 4, 6, 8, 10, 12; 4: 4, 8, 12; 6: 6, 12. The smallest common multiple is 12.

The GCF of two or more numbers is the largest number that divides each of the numbers without leaving a remainder.

List the factors of each number: Factors of 50: 1, 2, 5, 10, 25, 50; Factors of 100: 1, 2, 4, 5, 10, 20, 25, 50, 100. The largest common factor is 50.

The product of the GCF and LCM of two numbers is equal to the product of the numbers themselves.

Factor each number into primes, then take the highest power of each prime factor and multiply them together.

Factor each number into primes, then take the lowest power of each common prime factor and multiply them together.

Find the LCM of 9 and 15, which is 45 seconds.

To find the LCM of 3 and 5, list the multiples: 3: 3, 6, 9, 12, 15; 5: 5, 10, 15. The LCM is 15.

To find the GCF of 12 and 18, list the factors: 12: 1, 2, 3, 4, 6, 12; 18: 1, 2, 3, 6, 9, 18. The GCF is 6.