The biggest misconception that a competitive exam aspirant has in mind is that hard work is the only key to success. In order to crack a competitive exam like GATE, IES etc. one needs to understand and fulfill the demand of the examination. Over the years competitive exams have become even more competitive; in order to prevail in this environment an aspirant should make sure that his efforts are in the right direction. The birth of this book is based on the feedback of students who have succeeded in GATE and IES examination. As per them “there must be a single book for a single subject that should fulfill all the requirements of the exam, it must be the closest experience to a classroom coaching and should have enough problems to enhance the application of knowledge.” Thus we came up with this book “Industrial Engineering & Operation research” to help the readers in developing a strong concept of the subject. It has 25 years of solved questions of GATE and IES. Our books are linked with GATEMENTOR YOUTUBE channel. Short videos of lectures on Mechanical Engineering (GATE) have been provided, this will help the readers in developing a strong concept of the subjects. We at GATEMENTOR have a vision to guide the students in the most optimum way so that he could utilize his potential to the utmost. We hope this book will serve that purpose. Any suggestion from the reader are welcome. Visit our website for more information on GATEMENTOR and GATEMENTOR Publications. AND REMEMBER.....