Question 53153
Factors of 4: 2,2
Factors of 20: 2,2,5.
Highlight common factors:
4: 2,2
20: 2,2,5
Common factors: 2,2
The product of these common factors is:2*2=4.
This number, 4, is your greatest common factor:

Greatest Common Factor( 4, 20 ) = 4.
The product of 4 and 20, divided by the GCF 4, is .

So, 20 is the least common multiple of 4 and 20.