yaygmat
Could you please explain what do you mean by--
the mocks do not have Experimental questions, every question counts. In a real exam, only 30 of 36 questions count.
The mocks are scored out of 36 questions, the real exams out of 30.
In the real exam, the GMAC adds some questions that are not counted at all. People use various names for these questions: experimental questions, unscored questions, pre-test questions,.... When we take the exam, we do not know which questions are real counted questions and which are experimental.
Real questions start as experimental questions. Before any question is used as a real question, the GMAC needs to pre-test the question and collect information about it.
For example, if 90% of test takers get the question right, then GMAC will know this is a relatively easy question. If only 2% of test-takers get it right, then GMAC will know this is a hard question. Or perhaps, suppose high scorers get the question wrong and low scorers get it right, then the GMAC may think there is something wrong with the question and may decide not to use it at all. (BTW, some of this is guesswork. I don't know for sure.)
After pre-testing is done and the GMAC has collected the necessary information, the experimental question can become a real question in later exams.
This article has more information about experimental questions:
https://blog.targettestprep.com/gmat-ex ... questions/