While there is ample practice included with your GMAT Quantitative Course, many students use the GMAT Official Guide 2021 as an additional source of practice questions. However, the book's answer key isn't very helpful. In fact, it's downright confusing in most cases. That's why I recorded better answer explanations for every question in that book -- including the 262 Problem Solving questions and 240 Data Sufficiency questions. They explain not only WHAT the right answer is for each question but also HOW to get right answers on similar questions in the future.