# When can you use common multiples and factors?

Use the LCM when you are adding and subtracting unlike fractions. Use the GCF when you are simplifying fractions.

### What are the common multiples of 4 and ll?

To find the common multiples of two numbers, you first need to break them into their prime factors. In this case: 4 = 2x2 11 = 11 There are no common prime factors, and so we can say that the lowest common multiple is 11x4 = 44. In order to find other common multiples, we simply multiply this number by any integer, for instant 44x2, 44x3, 44x4, and so on. Following this rule, the first…