Math on the Go

Most people would say that mathematics is the art of calculating. The mathematician Christian Hesse thinks this is wrong or at least short-sighted. Math, he says, is the art of using thinking to make calculating unnecessary. He shows you how this can work by sharing the whole cornucopia of his magical calculation tricks for doing math in your head. They make calculating so simple that no one will be frustrated anymore and, in fact, they will find it completely effortless. Isn’t it super cool to be able to square even three figure numbers like 271 in your head in just seconds? Or to solve the daunting product of 396x178 in just a few quick steps without giving yourself a headache? Or to divide the mighty number 2134215 by 9 in a single short line? Or to pull the reciprocal of 19 from right off the top of your head decimal by decimal? Or to announce to an astonished audience which day of the week Christmas Eve, New Year’s Eve or your own birthday will fall on without looking at a calendar? All of this can be found between the covers of this book. It has been designed for not only those who want to improve their mental calculation skills—yes, even take them up to full-speed—but also for those who are interested in the ideas behind these tricks that make the mind-boggling possible. Christian Hesse holds a Ph.D. from Harvard University and has taught at the University of California, Berkeley. Since 1991, he has been a professor of mathematics and statistics at the University of Stuttgart. He has advised the German Bundestag, is an expert for the Federal Constitutional Court, and writes books. C.H.Beck has published several of his other works, including Das kleine Einmaleins des klaren Denkens. 22 Denkwerkzeuge für ein besseres Leben (The Little Guide to Clear Thinking. 22 Thinking Tools for a Better Life, 2013); Warum Mathematik glücklich macht. 151 verblüffende Geschichten (Why Mathematics Makes You Happy. 151 Amazing Stories, 2012); Was Einstein seinem Papagei erzählte. Die besten Witze aus der Wissenschaft (What Einstein Told His Parrot. The Best Science Jokes, 2013); Wer falsch rechnet, den bestraft das Leben. Das kleine Einmaleins der Alltagsmathematik (He Who Miscalculates Will Be Punished by Life. The Little Guide to Everyday Mathematics, 2014).