This book has received very good response from students and teachers within the country and abroad alike.Its previous edition exhausted in a very short time.I place on record my sense of gratitude to the students and teachers for their appreciation of my work,which has offered me an opportunity to bring out this revised Eighteenth Edition.Due to the demand of students a chapter on Linear Programming as added.A large number of new examples and problems selected from the latest question papers of various engineering examinations held recently have been included to enable the students to understand the latest trend.