Several readers have said they like my trick for finding the LCM described in the post “How to Find the LCM — FAST!” but wonder how to use the trick for finding the LCM for THREE numbers. Here is how you do that.
Essentially it involves using the same LCM trick three separate times. Here’s how it’s done.
Suppose the numbers for which you need to find the LCM are 6, 8, and 14.
Step 1) Find the LCM for the any two of those. Using 6 and 8, we find that their LCM = 24.
Step 2) Find the LCM for another pair from the three numbers. Using 8 and 14, we find that their LCM = 56.
Step 3) Find the LCM of the two LCMs, meaning that we find the LCM for 24 and 56. The LCM for those two numbers = 168.
And that, my good friends, is the LCM for the three original numbers.
So, to summarize. Find the LCM for two different pairs. Then find the LCM of the two LCMs. The answer you get is the LCM for the three numbers.
Here are a few problems that give you a chance to practice this technique.
Find the LCM for each trio of numbers.
a) 10, 25, 30
b) 16, 28, 40
c) 14, 32, 40
The LCMs for each trio are: