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This is a great resource. DO NOT rely on "Cracking the GMAT" from Princeton to succeed on the mathematics portion of the GMAT. The mathematics section in that book is woefully inadequate when compared with this. This math workout really teaches you how to think in an unorthodox manner employing both methodology and wide range of mathematical understanding, not in terms of depth, but breadth and how different types of math concepts link together. I would also recommend reviewing basic math to mid-level algebra before engaging with this text. But overall, great resource.
This book helped me remember how to solve exponential formulas and whatnot thats required for doing well on the GMAT but I needed to search elsewhere for some other problems, like YouTube. MyTeacher is excellent, btw. This books explain things in such jargon that its difficult to pick up on how to solve for something if youve never understood the math before. The GMAT committee needs to reconsider their approach on helping students better themselve.