GMAT Strategy

ok. first, i want to talk about the way in which you are approaching the material.
you have named a bewilderingly huge number of sources -- that's more books than i have ever used in my professional career, and i've been teaching standardized tests for 16 years!
this leads me to believe that your study strategy consists almost entirely of just DOING large numbers of problems, without spending as much time as you should spend on REVIEW.

remember: pure practice, all by itself, is not really going to pay off that much. you have to do practice problems and also get takeaways that you can apply to future problems.
i.e., you have to keep in mind that the problems that you are solving right now are not the point -- it actually doesn't matter all that much, in the long run, whether you are getting the practice problems correct or incorrect. the point is whatever lessons you can glean from those problems and then apply to FUTURE problems.

see here:
https://www.beatthegmat.com/need-retake- ... tml#190567

also here:
https://www.beatthegmat.com/need-tips-fr ... tml#107595

notice that these review methods apply just as much to problems that you got correct as to problems that you got incorrect. you should review the problems that you got correct -- including trying to think of OTHER ways in which you can solve them!
remember, it ultimately doesn't matter that you have successfully solved that particular problem -- you still need to rack your brain for other methods of solution, just in case you see a similar problem in the future. (you will not see another problem that is just like the one that you have finished!)

if you aren't doing this -- i.e., if you aren't spending a significant amount of time reviewing problems that you have gotten correct, in addition to reviewing problems that you have gotten incorrect -- then, ironically, these sessions in which you are getting 90% correct are probably the LEAST helpful sessions!
i.e., if you are just solving a problem and saying "good, i solved that", then this has no value at all for your preparation: it just verifies that you can solve problems that you already know how to solve.
the only way that you can build on these successes to help you with future problems, with which you otherwise would have had more difficulty, is to try to get takeaways as described in the posts cited above. this is not an easy process, but it is the only process that will make your studying ultimately worthwhile.

good luck!

oh, and i also wanted to make a brief comment about the goal that you have stated.

i think that 720 is a reasonable goal. however, i think that your originally stated goal of 750 is a little bit unrealistic (though not necessarily impossible) in light of your stated scores at the current time.
specifically, you have basically topped out the quant scale already -- you are already scoring consistently at the 49 level, so there is little if any room for improvement in quant.
in light of this fact, stated goal of 750 would mean picking up 80-100 points in verbal alone. that's hard enough to do, but, from where you are now (already in the high 600's), i have actually never seen it happen.

again, i don't want to say that anything is impossible, but i'm glad that you have reduced your goal score from 750 to a more achievable 720. doing so is definitely going to go a long way toward taking a lot of stress off your shoulders.

good luck.

Received a PM asking me to respond.

Yes to everything that Ron said.

So, you've changed your test date, giving yourself 2 more months. Good. You now have more of an idea of what you should be doing, also good. Read the below articles. They talk about HOW to do this review / analysis / finding the takeaways process that Ron discussed above.

https://www.beatthegmat.com/a/2009/10/09 ... ce-problem
https://www.beatthegmat.com/mba/2010/04/ ... our-errors

https://www.beatthegmat.com/mba/2010/03/ ... c-question
https://www.beatthegmat.com/mba/2010/01/ ... r-question
https://www.beatthegmat.com/mba/2010/02/ ... e-question

more frequent tests ( at least 10 )

No. Don't do that. That's just perpetuating the "do lots of problems" mentality rather than actually learning from what you've done. Maybe 10-15% of your learning comes while you're doing a problem. The vast majority of your (potential) learning comes AFTER you are done with that problem - it comes from everything you do to review and analyze that problem. On any problem (including the ones you got right), you should be spending 2 to 5 times as long to review it as you spent doing it in the first place.

CAT exams are really good for (a) figuring out where you're scoring right now, (b) practicing stamina, and (c) analyzing your strengths and weaknesses. The actual act of just taking the exam is NOT so useful for improving. It's what you do with the test results / between tests that helps you to improve.

If you have taken an MGMAT test recently, you can use this article to analyze your results. That will then help you develop a study plan - including going back over those questions to analyze - and that's where you're really going to learn!
https://www.beatthegmat.com/a/2009/09/23 ... tice-tests

As to whether you should study on your own or take a class / work with a tutor, there are advantages to working with a tutor or taking a class, yes, but those options are also expensive. A tutor can help to diagnose your weaknesses, make sure your study process is effective, direct your study plan in general, and so on. (Make sure you're working with someone who is capable of doing all those things. Don't use a tutor for "homework help" - that is, someone who just tells you how to do all of the problems on a list that you bring to the tutor. Such a list can be helpful as a jumping off point: Tutor, I'm struggling with this one, what do you think? But it shouldn't just be, "Oh, well the answer is C because of xyz. Next?")

You'll have to decide whether you think the potential benefits are worth the cost. I did write an article about this; here's the link:
https://www.beatthegmat.com/mba/2010/06/ ... s-or-tutor

The first part talks about how to make the choice for yourself and the second part talks about how to choose the best tutor or class instructor for you (if you decide to go that route).

but sometime when i get a tough SC question , i can't even figure out what to do to this question

That's true for everyone. One of the things that you have to "give up" when studying for the GMAT is the idea that you're going to learn how to get everything right. Nobody gets everything right, including those of us scoring in the 99th percentile. Sometimes, they're going to give you something that you don't know how to do.

If you're scoring 95th+ percentile in a section, that might only happen once or twice in a section.

If you're scoring lower than that, then you can expect this to happen multiple times - most people have to guess on between 4 and 7 questions per section. (This doesn't refer to times when you narrow down to 2 answers - that's actually pretty good progress on a problem.) When you get one of these, don't take extra time to make a guess. Learn how to recognize (and acknowledge) when the test has given you something that's too hard and then make your guess at or before the average time limit for that problem.

Next, if you're examining a problem and think, "Well, I really should have gotten this one / known how to do this one," your next task is to ask yourself WHY you didn't. What prevented you from taking the necessary steps to get to the right answer? Where, exactly, did you get off track? If it's verbal, WHY did you think the right answer was wrong and WHY did you think the wrong answer was right? (Now you know at least two new reasons why it's not good to eliminate an answer or pick an answer - whatever reasons you used to eliminate the right one and pick the wrong one.)

These things are all discussed in the articles that I linked to last time. Have you read those before? Have you tried doing that kind of analysis on your practice problems? That's where to start, and you should start doing this on OG problems - regardless of whether you have done them before. (While also reminding yourself that, no matter how good you get, you still aren't going to be able to do EVERYthing you see on the test. That's just not how this test works.)