How do you find the Least common multiple of 15, 20?

1 Answer

LCM = 60

Explanation:

Let's first find the prime factors of these two numbers:

#15=3xx5#
#20=2xx2xx5#

The LCM will have all the prime factors from the two numbers but we can drop replicates across the numbers we're doing this for. In this example:

From 15, we get both the 3 and the 5

From 20, we get two 2s - the 5 is already accounted for in the 5 from the 15.

The LCM is:

#2xx2xx3xx5=4xx15=60#

#15xx2xx2=60#
#20xx3=60#