The first 5 multiples of 4 and 20 are 20, 40, 60, 80, 100
The first five multiples of 4 are 4, 8, 12, 16 and 20. For them to be common, they need to be compared to another set of multiples.
The LCM is 20
20, 40, 60
20, 40 and 60
20, 40, 60
20, 40, and 60.
Yes.
They are: 20, 40 and 60
20, 40, and 60
20, 40, 60
20, 40, 60
140, 280, 420