@uniform
The formula 1.25(root of h1+ root of h2) is an approximation just like 1 by 60 rule.
The exact formula of calculating range of a Tx considers POwer, medium characteristics , frequency and more components which are not associated with Aviation. (must have read R=root (power))
So, the above mentioned formula gives you an approximate ans, choose whichever is near to that ans.
Theoritical and approximate ranges are same thing. I think its a no brainer, just to confuse. Only ques 4 sounds confusing in which ans comes out to be 281 but the ans given is different. I presume this as a mistake.
Fly Safe