Finding the Least Common Multiple of Three Numbers

Miacademy & MiaPrep Learning Channel

This math tutorial provides a clear, step-by-step demonstration of how to find the Least Common Multiple (LCM) for a set of three numbers: 10, 15, and 18. Building upon previous knowledge of prime factorization, the narrator guides viewers through creating factor trees for each number to identify their prime components. The video then transitions to a systematic method of constructing the LCM by combining these prime factors, ensuring each original number is represented within the final string of factors. The content focuses on the 'building block' approach to LCM, where students learn to identify which prime factors are already present and which need to be added. By breaking down 10 into 2 and 5, then checking against 15 and 18 to add necessary factors (a 3, and then another 3), the video visually demonstrates the logic behind the algorithm. This prevents the common mistake of simply multiplying all numbers together and highlights the efficiency of using prime factorization over listing multiples. This resource is highly valuable for middle school math classrooms introducing or reinforcing number theory concepts. It serves as an excellent model for explicit instruction, demonstrating good procedural fluency and checking for understanding. Teachers can use this video to transition students from finding the LCM of two numbers to more complex problems involving three or more numbers, helping to solidify their understanding of the relationship between factors and multiples.