Using C# reflection to call a constructor

I have the following scenario:

class Addition{
 public Addition(int a){ a=5; }
 public static int add(int a,int b) {return a+b; }
}

I am calling add in another class by:

string s="add";
typeof(Addition).GetMethod(s).Invoke(null, new object[] {10,12}) //this returns 22

I need a way similar to the above reflection statement to create a new object of type Addition using Addition(int a)

So I have string s= "Addition", I want to create a new object using reflection.

Is this possible?