How To: Find the lowest common multiples

Watchers of this video will learn how to find the "lowest common multiple", the lowest whole number that can be divided by each of two numbers evenly. For example, the lowest common multiple of 8 and 12 is the lowest number of which 8 and 12 are both factors. To find the lowest common multiple of 2 numbers, find the factors of both numbers. One way to do this is to make a "factor tree", drawing branches with factors from each number until it cannot be factored any more. Once both numbers are completely factored, cross off any numbers that are duplicated in both; for example, with 8 and 12, the factors are 2 x 2 x 2 and 2 x 2 x 3. Since 2 is found in both sets of factors, it can be crossed off. Since it is found duplicated again, another set of 2's can be crossed off. This leaves 2 and 3. Next, multiply the left over factors by the other original number (so 2 is multiplied by 12 and 3 is multiplied by 8). For both cases, the answer is 24, so 24 is the lowest common multiple of 8 and 12.