The first step to this method of finding the Least Common Multiple of 21 and 1 is to begin to list a few multiples for each number. If you need a refresher on how to find the multiples of these numbers, you can see the walkthroughs for those here:
Let’s take a look at the first 10 multiples for each of these numbers, 21 and 1:
First 10 Multiples of 21: 21, 42, 63, 84, 105, 126, 147, 168, 189, 210
First 10 Multiples of 1: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
You can continue to list out the multiples of these numbers as long as needed to find a match. Once you do find a match, or several matches, the smallest of these matches would be the Least Common Multiple. For instance, the first matching multiple(s) of 21 and 1 are 21, 42, 63. Because 21 is the smallest, it is the least common multiple.
The LCM of 21 and 1 is 21.
