When we learned adding and subtracting fractions, we learned that the number on the bottom, the denominator, has to be the same. In order to get a common denominator, we first need to find the Least Common Multiple (LCM). The LCM of two numbers is the smallest number that both numbers divide evenly. The video below will explain two methods of finding LCMs:

Least Common Multiple (LCM)

Video Source (08:44 mins) | Transcript

**The two ways to find the LCM:**

- Skip Counting
- List the multiples of each of the numbers given and find the smallest number in both lists.

- Prime Factorization
- Find all the prime factors of each number given.
- Create a new number that contains all the prime factors of each number. Remember to include multiples if there are multiples of the same factor in either prime factorization. Example: \(9 = 3 \times 3\) and \(15 = 3 \times 5\), since 9 has two 3s and 15 has only one 3 in its factorization, the combined list will need two 3s. The LCM of 9 and 15 is \( 3 \times 3 \times 5 = 45\)

## Additional Resources

- Khan Academy: Least Common Multiple (04:15 mins, Transcript)
- Khan Academy: Least Common Multiple with Repeating Factors (02:34 mins, Transcript)

### Practice Problems

**Find the least common multiple for the following pairs:**

- 5 and 6 (Solution
- 4 and 12 (Solution
- 6 and 10 (Video Solution
- 4 and 14 (Solution
- 7 and 9 (Video Solution
- 7 and 5 (Solution

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