How to become a lightning calculator

"How to Become a Lightning Calculator" by Anonymous is a practical guidebook on quick and efficient calculations, likely written in the late 19th century. As a mathematical manual, it focuses on techniques, shortcuts, and methods to enhance mental arithmetic skills, making it a valuable resource for students, professionals, or anyone interested in improving their numerical proficiency. The book offers a diverse range of strategies for addition, subtraction, multiplication, and division, all aimed at increasing speed and accuracy in calculations. It discusses methods for adding numbers quickly, including how to handle repeating figures and adding columns simultaneously. Additionally, the text covers multiplying numbers by specific values, calculating interest, making change, and understanding discounts, along with various tips and examples to aid comprehension. Ultimately, the book serves as a concise tool for mastering mental arithmetic, empowering readers with techniques to perform calculations with astonishing rapidity, akin to a "lightning calculator."