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This Number Trick comes from one of my students.   Unfortunately, I am unable to print his name on the internet.  However, he does know who he is and I thank him very much! This is a very useful trick to use when trying to figure out LEAST COMMON MULTIPLE or LCM.  So teachers take note.  This tricks works quite well.

Step 1:   First make an L shape (like an upside down long division sign) and put both numbers inside. For example: the LCM of 12 and 15.

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Step 2:   Find a number that can evenly divide into both numbers.  Place that number on the left of the figure.

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Step 3:   Then divide the number and place the answers under the numbers. If the numbers still have a common factor then repeat steps 1-3.

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Step 4:   Multiply all number that are outside the figure and that will be the LCM.

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Here's a second example:

    The LCM of 6, 12, and 18.  Here I had to repeat steps 1-3.

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Page by: Mathman (Bruce A. Titen) 1998