The lowest common multiple (LCM) of two whole numbers
is the smallest whole number which is a multiple of both. 

 

LCM Example

Consider the numbers 12 and 15 again:
 
The multiples of 12 are : 12, 24, 36, 48, 60, 72, 84, ....
The multiples of 15 are : 15, 30, 45, 60, 75, 90, ....

60 is a common multiple (a multiple of both 12 and 15), and there are no lower common multiples.
 
Therefore, the lowest common multiple of 12 and 15 is 60.