Question

Which is greater 4L or 4500 mL?

Answer 1

1 L = 1,000 mL 
Divide 4,500 by 1,000 to get 4.5 L
4.5 is bigger than 4, so 4,500 mL is larger than 4 L

Answer 2

4500 mL = 4.5 L
so 4500 is greater that 4 L