Secondary category, the most promising student group in the math olympiad, is a time to come out as a problem solver with more logical reasoning and analytical skills. This is the best time to practice more and more. To make the best use of time, this book carries 551 problems from the past years. Learners can find the problems arranged in different sections. Specially the problems of 2021 are also added here to make the preparation more up to date. The theory section contains most of the basic approaches and some advanced level theories which will help you to begin the journey in seeking deep knowledge in the world of mathematics. We hope every English version and medium curricula student will find it useful to get the concise idea of BdMO. Students will also find some useful links which will certainly help them remain ahead. This book is also a bucket listing one for any math enthusiast to find the beauty of math.