Least Common Multiples

Practice computing least common multiples

These worksheets provide practice in a very important mathematics skill, which is computing the least common multiple (LCM) of two numbers. A prerequisite to finding LCMs is being able to decompose an integer into primes, so if students are not good at this yet then this one may be over their heads.

Finding an LCM is a three step process, but all three steps are documented in the answer page that accompanies every LCM worksheet. First, both numbers need to be decomposed into their prime numbers. Next, the smallest set of primes that can be used separately to construct each number is assembled. Finally, the product (multiplication together) of all of these primes is the LCM. An LCM will never be less than the larger of the two numbers, and will never be more than their product.

There will probably be a lot of confusion between LCMs and Greatest Common Factors (GCFs), as the steps and purposes are similar. It would be a good idea to come back to both of these skills repeatedly over time in order to reinforce these skills.