Hey,
Good news is that your verbal score is decent!
I believe that many people in the forum will suggest the
MGMAT Quant guides if your quant skill is rusty. Honestly, I didn't use all the
MGMAT quant books and personally think
MGMAT Number properties and Word translation are the best. When you read the books, you should practice the problems in OG12, which are listed in each chapter. Oh, by the way, have you ever looked at the GMATClub Math book?
gmat-math-book-87417.html I am always a big fan of this material and find it very helpful in my prep.
I agree that the difficulty level of quant problems in OG12 may not on par with that on real test, but the concepts tested are the same. IMO, your approach to OG12 problems should be (i) not to focus too much on difficulty level of a certain quant question, but (ii) to understand and master the underlying concept(s) - which specific knowledge(s) you are being tested. An
error log should be useful to help keep track of your practice and figure out your deficient areas.
Best of luck!
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There can be Miracles when you believe