paulstrike wrote:
I need 15th percentile in verbal and 75th percentile in Quant, how many questions do I need to do in order to achieve that? Thanks for your information chart

Do you mean how many questions do you need to get right in each section in order to achieve those percentiles?
No one can give you an exact answer to that question. The way that the exam is scored is the first section of each type (Quant and Verbal) is used to determine the difficulty level of the second scored section of each type.
So if you do well on the first Quant section and you get the hardest second section of Quant you may only need to get 50% of the questions right in that second section to get the 75th %ile. So that might mean that you get something like 28 out of 40 correct.
However if you miss more questions on the first section you will need to get just about everything right on the easier second section in order to get that same 75th %ile. So maybe you miss six or seven questions on the first section and then you need to get 19 of 20 right on the second section. So then you are getting 32 out of 40 for the same score.
And if you miss enough questions on the first section then the difficulty level of the second section will be low enough that you may not be able to attain the 75th %ile even if you get a perfect 20 out of 20 on the second section.
As to the 15th percentile on Verbal. Well this will not require you to get even half of the questions right. In fact, you could really figure out which type of question that you are best at - either Reading Comprehension or the "Vocab" questions and focus your attention there.
And do remember that there will be one additional unscored section. This means that you will get either an extra Quant section or an extra Verbal section so that you will get 3 of the 20 questions sections of that type and one of those three sections does not count. So when we speak of the number of questions you need to get right keep in mind that none of the questions you get in that unscored sections count.
For example your exam might go AWA essay #1, AWA essay #2, Quant 1, Verbal 1, Quant 2, Verbal 2, Quant 3. In this scenario both Verbal sections would count towards your score, but one of the quant sections does not count while the other two do. It is impossible to tell which section is the unscored one so you have to try you best on all five sections.
Hope that provides the beginning of an answer let me know if you have follow-up questions!
_________________
David Newland
Veritas Prep GRE Instructor