Used degree complement I am not sure of 中国的发展速度比美国的快得多

I am not quite sure if this is grammatical or not.

I used 快得多 to describe speed of development is faster.
You are already correct! Some alternatives, you can also use Adj.+多了 or Adj.+很多 to express the degree is high. So, all of these sentences have the same meaning.


  
  中国的发展速度比美国的快得多。
  中国的发展速度比美国的快多了。
  中国的发展速度比美国的快很多。