Short-Cut Math

by Gerard W. Kelly

Clear, concise compendium of about 150 time-saving math short-cuts features faster, easier ways to add, subtract, multiply, and divide. Each problem includes an explanation of the method, a step-by-step solution, the short-cut solution, and proof, as well as an explanation of why it works. No special math ability needed.

Genres: Mathematics, Nonfiction, Reference, Education, Science

158 pages, Kindle Edition

First published January 1, 1969

Reviews

[Bram · Rating 2 out of 5]

Book with some tricks on how to add/substract/multiply/divide. Almost all the "tricks" are very, very basic, however, there were a few tricks that I didn't know before.

Even though several publishers sell this book, the ebook is freely available: http://archive.org/details/Short-cutMath

[Ben Gutierrez · Rating 5 out of 5]

I thought I knew a few things about calculating quickly. I suppose I did, but there are some that I never sussed out. Good examples are multiplying large numbers that are kind of close but not quite the same, multiplying numbers by teens, that sort of thing.

Not all of the proofs help build intuition. Visualizations would have helped. Since this book covers only addition, subtraction, multiplication, and division, you should be able to imagine arranging the numbers into rows and rectangles. This will make things clear and help you remember the rules.

Dover books all have issues with typesetting in ebooks, especially when there is math. This book is no exception. Be prepared to read carefully and imagine what the text is supposed to say.

[Kirk · Rating 4 out of 5]

Handy refresher on arithmetricks I learned in middle school, except casting out 9s. I can never remember that one. It's like using a baitcasting reel: I get mental backlash.

"Idiot's Guide: Speed Math" by Gaurav Tekriwal includes many of the same shortcuts. It also includes practice problems and Vedic tips for finger multiplication, powers of 2, 3, 4, and 5, and square and cube roots. If I were buying, it would be a better deal. But the library only carries this book, and "free is a very good price."

[Shu · Rating 3 out of 5]

It was fun getting quizzed on by my 8-year old daughter as she flipped through this short book while I was driving. It was also fun to spot the mathematical reasoning before arriving at the "Why it works" section at the end of each shortcut method. I would have enjoyed the book more if each chapter included a list of applicable math problems for one to test one's grasp of the concepts as well as to develop pattern recognition skills / affinity to numbers. Maybe an app or a game could help.

[Daniel · Rating 3 out of 5]

Some of the short cuts in this book were new and helped me save time when calculating, others are very common sense and basic. There are alot of short cuts however in some cases when you actually need to calculate things quickly, remembering the short cut and then running through the steps of the short cut would actually take longer than just doing a simple left to right calculation. This book could also use some more exercises for practice.

[Madeline · Rating 5 out of 5]

basic shortcuts like shifting (36+44 = 40+40 or 12 times a number is 10x a number plus double), aliquot parts (which I had figured out before reading this book), divisibility rules, how to check your work, quite a bit on casting out 9's which was kind of weird...

fun fact for anyone reading this review... numbers can be squared easily with binomial expansion (eg, 37^2 = 30^2+30*7*2+7^2 = 1369) - that trick wasn't in this book, but is quite helpful

[Alain W · Rating 3 out of 5]

Good book to refresh your mental math ahead of an aptitude test.
I only wished the book had some exercises at the end of each chapter like secrets of mental math by A.T. Benjamin had, in order to fully apprehend the material.

[Daniel · Rating 5 out of 5]

A comprehensive, well structured book of techniques.

[Nabil Khalil · Rating 3 out of 5]

Very basic

[Kevin Demel · Rating 2 out of 5]

This book had a lot of hints about how to do math calculations quicker in your mind

[Jordan · Rating 3 out of 5]

Font is a nightmare and clearly from a 60s textbook but otherwise good info.

[Michael Pearce · Rating 5 out of 5]

Excellent maths book

I love reading and doing the maths in this kindle book, everything is laid out in a way that's easy to follow, I would recommend it to everyone.

[Abhiram Naik · Rating 4 out of 5]

Excited about it now the book will be insider

[Roger · Rating 3 out of 5]

Not a bad book. Worth a quick read to learn some basic math tricks.