The least common multiple (LCM) of two or more numbers is the smallest number that is a multiple of each of those numbers. For example, the LCM of 4 and 5 is 20 because 20 is the smallest number that can be evenly divided by both 4 and 5. Finding the LCM is useful in various mathematical problems, especially when adding or subtracting fractions with different denominators. To find the LCM, one can list the multiples of each number and identify the smallest common one. Alternatively, the LCM can be calculated using the prime factorization method or by using the relationship between the LCM and the greatest common divisor (GCD). Understanding the LCM helps in solving problems involving fractions and ratios.