I’ve classified all the quantitative problems in the 2017, 2018, and 2019 Official Guides based on content. Many of these problems are hyperlinked to complete solutions that take more of strategic approach than what you’ll see in the solutions provided by GMAC. In the future I want to provide a classification based on common strategies and tactics that skilled test-takers use on a regular basis. I’m also planning to do the same for the verbal questions – esp. sentence correction. As I add more solutions, I’ll also do something to indicate which problems don’t appear in later official guides.