Secrets of Mental Math: The Mathemagician's Guide to Lightning Calculation and Amazing Math Tricks

This is a fun book for adults and children who like math and convenient mathematical tricks that will allow to quickly solve a variety of math problems in your head. This book makes math fun! Recently I visited family in Chicago. My great nephew is inquisitive and is advanced in math. Our mutual love for math makes it very easy to communicate with this youngster. Although he is only 10, I was able to teach him one of the tricks in the book that most adults do not know. If you want to square a two-digit number that ends in five, the last two digits always end in 25. To discover the digits that come before 25, multiply the first digit by itself and add the first digit to it--for example 35 x 35, 3 x 3 + 3 = 12, so 35 squared = 1,225. Another example is 95 squared. 9 x 9 +9 = 90, so 95 squared = 9,025. There are 231 easy to follow pages in this engaging book with numerous tricks and problem solving techniques with answers that follow the problems or in the back of the book. Though my great nephew is hampered by a medical condition that is not conducive to good communications with some people, his math skills are far beyond his age. I know that he will be intrigued and have a blast with this book and can hardly wait for him to use it. This book will not only make you seem smarter, it will make others think you are a mathematical whiz and they will be correct. Math can be and is fun when you master books like this one. Enjoy! I recommend Secrets of Mental Math by Arthur Benjamin and Michael Shermer to friends, family, and others who would like to increase their mathematical skills in a fun and easy manner.

I'm a near-geezer age character and long removed from the academic, high level mathematician rigor. I remain operationally proficient in Mathematica to work that occasional problem when I need an answer without having time to revisit the physical, chemical or mathematical process. This book is not about mathematics but arithmetic. If you're in science or business, you are an arithmetician by trade. High speed, close enough mental arithmetic is critical to the trade. Simple arithmetic remains the great divider in critical thinking from those that can think and those that stumble. If you stumble, you know you stumble. I know mathematicians that can't balance a check book or conceptulize GAAP P&L or Balance Sheet mechanics. I've imagined myself a seasoned veteran in `close enough' mastery of columnar data, formula application, and simple arithmetic operations of a rote nature. I can determine the `range and unit measures' of the correct answer to a particular problem by the problem statement. It takes a lifetime to develop this skill from the rote arithmetic I should have paid more attention to it in elementary school, but ... it is what it is and it has to mastered. If you need a `correct' answer to 2 decimal places, use a calculator or Excel. If you need a fast approximation in the heat of mentally exploring alternatives use significance and proportionality to estimate within 5-10% of the calculated answer. That's usually performing well enough for fast critical thinking purposes. Remember that the equipment or source that provided the initial data is doing pretty well if it's within 5% of ground truth. In `Secrets of Mental Math' you can explore refining your arithmetician skill to 2 decimal places with only slight change ups in heuristic application. Why isn't this stuff taught in schools? I mean it is important to know why arithmetic works, but for gosh sakes ... can't education get to the chase and deliver the shortcuts (all mathematically based in the philosophy of mathematics) to get an answer using outside of the box methods? No one can be `damaged' by exposure to these methods. "Secrets of Mental Math" is an excellent consolidation of shortcuts and tricks to tune up you arithmetician trade. Our kids would benefit greatly if this or a similar text was included in a mandatory high school course called `Critical Thinking'. It would be a powerful primer for those that will never do a long division by hand again and for those that will go on to calculate chemistry and physics methods and equations. The answer is in the problem. Arithmetic is a tyranny. Do your kid and yourself a favor and try this powerful little book.

This is great! I bought it for my grandchildren, but I’m reading it!!!

Gave these out as end-of-the year rememberances to the 4th and 5th graders at an elementary school Math Pentathlon club. Next year, if I can find a sponsor, I plan to hand them out as the beginning of the year as de facto textbooks for that age. Used it over the year to teach how to do math in their heads to make them faster at the games. Usually took 10-15 minutes at beginning of club meeting to work on mental tricks, mostly from this book (or Khan Academy), and an hour and a quarter practicing the five games which are part of the Math Pentathlon competition. In one school year with once per week after-school practice, my group wasn't able to get too deep into the weeds. But the instruction piece really helped their level of competitiveness on the games, especially learning to add and multiply (relatively) large numbers in their heads. The trick about multiplying by eleven alone will delight even a struggling math-o-phobe. Some parts are well-written, some a little dense and repetitive. Getting good at these tricks really does require practice (along with already knowing one's multiplication tables). But if parents are putting time in at home to practice them with their kids, the payoff would happen pretty quick. Very useful techniques, once mastered. Just reading this book won't make you better at math. But reading it and doing all the practice activities will. You'll get out of this book what you put into it.

This book is about the important and today much forgotten skill of doing math in your head instead of on your phone. A good way of keeping your mind sharp and nimble.

Un très bon livre qui regorge d'astuces pour calculer toujours plus vite et sans papier, ni crayon, ni calculatrice. Pour ceux qui seraient rebutés par l'idée d'acheter un livre en anglais, le vocabulaire employé est très simple à comprendre.

My mental arithmetic was fairly good before purchasing this book but I wasn't exceptionally quick so I looked for some help in speeding things up. While reading this book I discovered I had been using the right to left paper method rather than using a left to right method. It's brilliant and works so fast. I actually feel cheated that I wasn't taught this stuff at school as it makes it so much easier. I will definitely be using this to help my kids mental arithmetic improve too. Awesome!

muito bom esse livro! agora consigo fazer muitas contas de cabeça.

Zwei 3-stellige Zahlen im Kopf multiplizieren? Kein Problem. Das Buch zeigt einige grundlegende Ideen, wie man sich das Kopfrechnen erleichtern kann. Mit dem kleinen Einmaleins, einer Hand voll Vereinfachungen und einen System zum Umwandeln von Zahlen in Worte (die man sich leichter merken kann) erscheint fortgeschrittenes Kopfrechnen nicht mehr wie Zauberei. Man kann die Regeln recht leicht umsetzen und erlebt ständig neue Erfolgserlebnisse. Das System zum Merken von Zahlen ist für Deutsche etwas ungeeignet, weil es sich auf die Buchstabenverteilung (und Phonetik) des Englischen bezieht. Man kann sich mit wenig Mühe aber auch ein eigenes System ausdenken, dass besser zur deutschen Sprache passt. Einen nachhaltigen Eindruck hat das Buch bei mir allerdings nicht hinterlassen. Oft ist der nächste Taschenrechner doch zu nahe und der PDA speichert Telefonnummern so zuverlässig, dass man weder auf Kopfrechnen noch auf Erinnerungshilfen angewiesen ist. Man weiß jetzt aber, dass man auf diese Helfer verzichten könnte, wenn man wollte. Ich habe mir übrigens das englische Buch geholt, weil die Sprache für mich kein Problem ist, die deutsche Übersetzung nicht so gut sein soll und das englische Buch wie immer preiswerter ist.