This book is designed to be used in conjunction with the Official Guide for GMAT Review, 12th Edition. In the Official Guide Companion, each math question is broken down and explained by our expert instructors, who not only have 99th percentile scores, but years of experience teaching the GMAT. The explanations in this book provide detailed, step-by-step approaches to every Problem Solving and Data Sufficiency question in the Official Guide. Where appropriate, the Official Guide Companion also details more than one way to arrive at the solution. And perhaps most importantly, all explanations are accessible and provide a framework for answering the particular question as well as similar questions you may see on the real test. Purchase of this book includes one year of online access to 6 full-length, computer-adaptive practice exams and the Official Guide "Archer."