The LCM of 12 and 27 is 108. To find the LCM of two numbers, we need to find the multiples of each number and then find the smallest multiple that is common to both numbers. The multiples of 12 are 12, 24, 36, 48, 60, 72, 84, and so on, while the multiples of 27 are 27, 54, 81, 108, 135, and so on. We can see that the smallest multiple that is common to both 12 and 27 is 108, so this is the LCM of 12 and 27.