First published in 1900, this classic manual to mental arithmetic offers practical techniques for performing quick calculations in one's head. Written by J.A. Henderson, a renowned accountant and teacher of mental arithmetic during the early 20th century, this book is a must-read for those interested in improving their math skills. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.