6th-Grade Math Word Problems - ThoughtCo For the first problem on this worksheet, you need to know that the factors of 12 are 1, 2, 3, 4, 6, and 12; and the multiples of 12 are 12, 24, 36. (You stop at 36 because the problem says that this number is the least common multiple.) Let's pick 6 as a possible greatest common multiple because it's the largest factor of 12 other than 12.