Well say for example that you have two numbers such as 3 and 6, and you try to do the least common multiple i would assume it would look like
3 6 9
6 12 18
if one number is a multiple of the other then it is automatically the least common multiple. In this example the least common multiple is 6. If this does not suffice or make sense then please comment and try to make your question more clear so i can help you.