This area has the same exactness as pure mathematics has?!

[MBSR]

Hi!
I have a doubt about one phrase.
A friend of mine corrected my phrase: "This area has the same exactness pure mathematics has" into "This area has the same exactness as pure mathematics has".
Is it right?
I thought it should have been : "This area has the same exactness as mathematics".

 

[Shoreditch]

This area has the same exactness as pure mathematics. :tick:
This area has the same exactness as pure mathematics has. :tick:
This area has the same exactness pure mathematics has. :cross:
This area has the same exactness pure mathematics. :cross:

No teacher, wait for them.

 

[probus]

I cannot to agree with Shoreditch in this case. The third statement is fine. Only the fourth is incorrect, although the second sounds slightly unnatural.