The lowest, or least, common multiple of 4 and 6 is 12. This is the smallest number that is a multiple of both 4 and 6.
One way to find the lowest common multiple, or LCM, is to first reduce each number to its prime factors. A prime number is a number that has only 1 and itself as factors. For the number 4, 2 squared, or 2 x 2, is the prime factor. For the number 6, 2 and 3 are prime factors. Take the largest power of each of the prime numbers that appears in either of the original numbers. Because 3 appears only as a multiple of 6, that must be included. Both 2 and 2 squared are multiples, but use 2 squared because it is larger. Multiply the squares together: 3 x 2 x 2 equals 12.