Higher Secondary, the top tier of college level learning, is full of different academic theories and advanced level knowledge. Students learn many topics and many methods to solve different real life and analytical problems. BdMO aims to unleash their inner learning about the core topics of mathematics so is the book. The 551 problem collection is lucrative to solve and fun to learn. We tried to touch geometry, algebra, number theory, combination and logic in a categorised way. As the horizon is infinite in the field of mathematics, learners should focus more on solving problems in a systematic way. This book has some theories which will connect the dots of their learning with the problem sets given. English version and medium students can be more benefited from this book to make a good practice for the BdMO. Problem sets of 2021 are added to this book which is a cherry on the top. Our basic aim is to provide a concise idea on the math olympiad approach and to make a generation with more problem solving skills.