Each question in the QPack 1 and the default set (the 90 questions that are available in GMATPrep for free) has an unique 5 digit question number. For example, a SC question ID would look like VSC01783.
The ID VSC01783 says, the question is from
1) Verbal pool - V
2) Sentence Correction sub pool - SC
3) ID number - 01783
Similarly, examples of PS, DS, and CR are QPS05678, QDS04789, and VCR03498, respectively.
Grouped questions have a little different format. A group of reading comprehension questions is numbered from VRC00198-01 to VRC00198-05, in which the -XX part indicates question number related to the passage 00198.
Integrated reasoning questions may come in group as well as in standalone flavors. An Integrated reasoning questions ID starts with an IIR tag.
Interestingly, the IIR IDs are between two to three digits, for example IIR00034, IIR00125, etc. From this fact, I assumed
that the question ID reflects the sequence in which it was created. For example, I assumed
that question VSC01783 is older that question VSC0345.
As I said before, the SC questions in QPack1 range from 1000 to 3000, whereas the default set contains SC questions in the 7000 range. If my assumption is correct, it can be inferred that the SC questions in QPack 1 are older than the default set. On the other hand, the quant questions appear to be newer.
(All the question numbers used in the post are randomly created by me.)
(I also assumed that the 5-digit ID number has one more part in it. I think the first three digits indicate an exam code and the last two digits represent the question number within the exam. For example, VSC01783 means Verbal - Sentence Correction - Exam Code 017 - Question 83 and VRC00198-01 means Verbal - Reading Comprehension - Exam Code 001 - Passage 98 - Question 01. However, this assumption is not needed for the inference above.)
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