Before you dive into it, why don't you download GMATPrep
and see how your score looks right now.
Based on your background, Math should not be an issue. You can probably master it with OG, though it does not provide strategies or much of concepts/formulas behind the problems. Since you have just 6 weeks, you may want to grab Kaplan math Workbook
- you should be able to go through it in 2 weeks and get a more comprehensive coverage than from OG
Then you can get PowerScore CR
book and Manhattan SC and Manhattan RC
books though since time is short, perhaps PowerScore Verbal Bible
will be a better choice - it is still a 450+ page book but it is shorter than those 3 combined.
The manhattan book will come with 6 tests (there is a code in the book that you enter online) Spend the last week or two taking the tests.
This assumes you want a 700+ score and have good foundation in Math and Verbal. If you need less, then you can chop things here and there. If more then it is a slightly different and longer story. Take the diagnostic test (GMATPrep) and see how you do. maybe you already have 700
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