I just published the video explanations to all of the 550 quantitative reasoning questions in the GMAT Official Guide 2021, which was released as an ebook in late April 2021. The physical official guide is due to be released on 3rd June 2020. There are 262 Problem Solving questions and 240 Data Sufficiency questions. Out of these 502 questions, 42 are newly released. The remaining 48 questions are available as part of the GMAT Online Question Bank. These 48 questions formed the diagnostic test in the 2020 GMAT Official Guide and older editions.