The least common multiple (LCM) of two or more numbers is the smallest number, other than zero, that is a multiple of all of them at the same time. In other words, it is the first number that appears in the multiplication tables of all of them. For example, the LCM of 4 and 6 is 12.
How to calculate the LCM of 4 and 6
One simple way is to list the multiples of each number until you find the first one they share:
- Multiples of 4: 4, 8, 12, 16, 20, 24...
- Multiples of 6: 6, 12, 18, 24...
The first multiple that appears in both lists is 12, so the LCM of 4 and 6 is 12. Another way is to break each number into prime factors: 4 = 2×2 and 6 = 2×3; the LCM is found by multiplying 2×2×3 = 12. Do not confuse the LCM with the greatest common divisor (GCD), which looks for the largest divisor, not the smallest multiple.
Why does the LCM matter for kids?
The most common use of the LCM is to add and subtract fractions with different denominators: to add 1/4 + 1/6 you find the LCM of 4 and 6 (which is 12) and use it as the common denominator. It also helps solve real-life problems, such as figuring out how often two buses that run at different intervals arrive together, or when two lights blinking at different rates turn on at the same time again.
The LCM is learned in elementary school, around 5th or 6th grade, and stays with students throughout middle school. Want your child to master math step by step? Book a free masterclass with an Algonova teacher.
