20
20 is the lowest common denominator for 4 and 10.
A common denominator? 1960000, for example. The LCM is 140.
It is: 100
60 is the least common denominator of 3 4 5 6 10 and 15.
60
20
100
It is: 100
It is: 180
It is: 180
100
The greatest common denominator of any set of integers is infinite.