Yes - it is recommended that you practice all the questions from the Official Guide 12th edition AND the Verbal + Quant supplements. However, this might not hold true in some conditions - say you are hitting your target GMAT score consistently on the GMATPrep tests, and feel you are comfortable/confident on the topics.

The Official Guide and companion supplement do not overlap any questions. However if you are using any previous edition of the Official Guide then there will be repeats. I have provided the difference between the current and previous editions of the OG here:

https://www.crackverbal.com/blog/og-11th ... th-edition

HTH,

Arun

Hey, great question and hopefully I'm not stepping on Arun's helpful reply at all, but given what you asked I really wanted to chime in.

In my opinion, far, far too many students focus their study efforts on the WRONG metrics:

-How many questions they've done
-How many hours/months they've studied
-Which or how many books they've read

What really matters is what you've learned and how well you're ready to perform on the test. And that you'll really only be able to gauge by taking inventory of:

-How are your practice tests coming along? Not just in terms of score, but how you feel...how are you pacing yourself? Are you missing questions because you just don't know how to do them, or because you're letting yourself get away with careless mistakes and the kinds of things that can be quickly fixed?

-How comfortable do you feel with each question type? Can you anticipate the kinds of traps that the GMAT is laying for you in Data Sufficiency questions? Are you systematic with the way that you approach Sentence Correction?

In order to be ready to take the test, you need to think deeper than "I've done all the OG problems". I'd much rather you're able to say "after doing 50 Data Sufficiency problems, I know that I need to ___________________ and make sure not to _____________" than say "I've done every DS problem in the OG and I got about half of them right". What good does the latter phrase do you if you haven't thought much about WHY you've gotten them right or wrong, or what that might mean for the future?

I'm kind of a weird example, but I doubt I did much more than 25 problems of each type before I took the GMAT. But in that time, I really clicked with Data Sufficiency...I had a feeling that the GMAT would try to trap me with "special case" numbers like negatives, nonintegers, and zero. I kind of knew that C was a fool's gold answer because of the "...but NEITHER ALONE" qualifier, meaning that if it seemed obvious that both statements together would solve the problem, I'd need to try to get it done with one of them alone.

On the flip side, I've had students come to me after having done the entire OG and still not really understand the Data Sufficiency format at all, with misconceptions like "since there are two variables here I can't possibly solve for whether x is positive since I don't know what x is".

What's really important is the QUALITY of the time you spend, not the quantity. The OG is a phenomenal resource, but don't make "completing the OG" your primary goal. If you struggle with the first 1/3 of problems in any section, put the OG down and get to work on those problems or concepts with other resources. OG questions are far too valuable to just plow through without knowing what you're doing. If you're doing well through the first half of most sections, take a practice test to see how you do when you're under timed pressure, or when you're getting questions in various orders. It's tougher to master Sentence Correction when you're seeing 2-3 SC problems followed by a long RC passage followed by a tough CR problem followed by an SC problem again - when you're only doing SC you get into an easier rhythm.

So...in summary, work smarter, not harder. If you do 1/3 of the problems in the OG but learn something from every question, that's exponentially better than doing all of the problems in the OG and not being able to hang your hat on really anything that you took away from them.