Methods for mental calculation and insight in numbers

Written by two of the world's foremost authorities on mental calculation, The Mental Calculator's Handbook is essential reading for aspiring calculating prodigies. From multiplying fractions to extracting square roots, all the techniques are presented and explained in a clear and rigorous way.

An antidote to mathematical rigor mortis, teaching how to guess answers without needing a proof or an exact calculation. In problem solving, as in street fighting, rules are for fools: do whatever works—don't just stand there! Yet we often fear an unjustified leap even though it may land us on a correct result. Traditional mathematics teaching is largely about solving exactly stated problems exactly, yet life often hands us partly defined problems needing only moderately accurate solutions. This engaging book is an antidote to the rigor mortis brought on by too much mathematical rigor, teaching us how to guess answers without needing a proof or an exact calculation. In Street-Fighting Mathematics, Sanjoy Mahajan builds, sharpens, and demonstrates tools for educated guessing and down-and-dirty, opportunistic problem solving across diverse fields of knowledge—from mathematics to management. Mahajan describes six tools: dimensional analysis, easy cases, lumping, picture proofs, successive approximation, and reasoning by analogy. Illustrating each tool with numerous examples, he carefully separates the tool—the general principle—from the particular application so that the reader can most easily grasp the tool itself to use on problems of particular interest. Street-Fighting Mathematics grew out of a short course taught by the author at MIT for students ranging from first-year undergraduates to graduate students ready for careers in physics, mathematics, management, electrical engineering, computer science, and biology. They benefited from an approach that avoided rigor and taught them how to use mathematics to solve real problems. Street-Fighting Mathematics will appear in print and online under a Creative Commons Noncommercial Share Alike license.

Do high-speed, complicated arithmetic in your head using the Trachtenberg Speed System. Ever find yourself struggling to check a bill or a payslip? With The Trachtenberg Speed System you can. Described as the 'shorthand of mathematics', the Trachtenberg system only requires the ability to count from one to eleven. Using a series of simplified keys it allows anyone to master calculations, giving greater speed, ease in handling numbers and increased accuracy. Jakow Trachtenberg believed that everyone is born with phenomenal abilities to calculate. He devised a set of rules that allows every child to make multiplication, division, addition, subtraction and square-root calculations with unerring accuracy and at remarkable speed. It is the perfect way to gain confidence with numbers.

No author has gone as far as Doerfler in covering methods of mental calculation beyond simple arithmetic. Even if you have no interest in competing with computers you'll learn a great deal about number theory and the art of efficient computer programming. —Martin Gardner

The remarkable system of Vedic mathematics was created after careful study of ancient -Sanskrit texts early last century. The Vedic system with its direct, easy and flexible approach forms a complete system of mental, mathematics (though the methods can also' be written down) and brings out the naturally coherent and unified structure of mathematics. Many of the features and techniques of this unique system are truly amazing in their efficiency and originality. Being a mental system, Vedic Mathematics encourages creativity and innovation. Mental mathematics increases mental agility, improves memory, the ability to hold ideas in the mind and promotes confidence, as well as being of great practical use. This course consists of three textbooks an Answer Book and a Teacher's Guide. The course is aimed at 11-14 year old pupils though some of it is very suitable for children from 8 years. Vedic Mathematics is being taught in many schools world-wide with great success: many top mathematics prizes have been won by students of this system.