Least Common Multiple

To find least common multiple you can use one of two methods (unless we specifically want you to find it by a certain method):

Method 1 - the listing method
1. List out the multiples of each number and find the smallest common multiple between the two.

Ex. Find the LCM of 20 and 24
20 - 20, 40, 60, 80, 100, 120, 140, ...
24 - 24, 48, 72, 96, 120, 144 ...

You will notice the LCM is 120 because it is the smallest common multiple

Method 2 - the prime factorization method

Find the LCM of 20 and 24 using prime factorization:
1. Make a factor tree for both 20 and 24
2. Multiply the highest power of each factor.

Ex. 20 = 2 * 2 * 5 or 2 to the second power times 5
24 = 2 * 2 * 2 * 3 or 2 to the second power times 3

So the LCM would be:
LCM = 2 to the third power times 3 times 5 or:
8 (2 to the 3rd power) * 3 * 5 = 120