Arithmetic Grade Five

Lesson Ninety-five: Least Common Multiples

Now we're to the point where we need to know how to find LCM's in order to solve the next group of fraction problems. First we will review how to find LCM's and then we will get into what they have to do with solving fraction problems.

Least Common Multiples
Finding the Least Common Multiple (LCM) of two numbers is quite similar to finding the GCF. Here are the steps for finding the LCM of 6 and 5.

Step One: List a few multiples of each number:

5: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 ...
6: 6, 12, 18, 24, 30, 36, 42, 48, 54 ...

Step Two: Find the first match. In the case of 6 and 5, the first match is 30. So, that's your answer.

Here's another example 


  FIND THE LCM OF 4 and 8:

  STEP ONE: List some multiples of each number.

    4: 4, 8, 12, 16, 20, 24, 28, 32 ...
    8: 8, 16, 24, 32, 40, 48, 56 ...

  STEP TWO: Find the first match.

       8
Now you get to try a few

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