REVIEW: "Magic Numbers"

You think math is boring, useless and is not able to generate interest? Maybe you're right. However, if you remain unconvinced, read the "magic numbers"? This book will turn mathematics into pure magic and will allow you to perform complex calculations in mind.

I love books with a bunch of useful and accessible presentation of information. They do not need to seek out the right idea of ​​the author between the lines to guess what he wanted to say, and try to find wisdom wherever it may be. Such books are good because sometimes you just want to get the most useful information and go ahead. After all, we are not always interested in reasoning and thoughts of the author.

With this review, I decided to do the same as Arthur Benjamin and Michael Shermer did with his book. Maximum of useful information and a minimum out-thought and reasoning. Actually, there is nothing to discuss here.

Arthur Benjamin

Professor of mathematics at Harvey Mudd College and a professional magician. He received his doctorate of mathematical sciences at Johns Hopkins University in 1989. In 2000, the Mathematical Association of America awarded him the Haimo Award for Excellence in Teaching. He is also a professional "matemag" and often appears in the "Magic Castle" in Hollywood. In 2005, Reader's Digest named it America`s Best Math Whiz (free translation: "the best American mathematician-scientist").

instagram viewer

Michael Shermer

Editor and columnist of the magazine Scientific American, publisher of Skeptic (www.skeptic.com), executive director of the Community of skeptics and the head of the course of public scientific lectures at Caltech. He is the author of numerous scientific books, including Why People Believe Weird Things ( «Why people believe weird things»), How We Believe ( «How do we We believe »), The Science of Good and Evil (« Science of Good and Evil »), The Borderlands of Science (« frontier science ") and Science Friction (« Scientific contradictions ").

What awaits you

The authors teach raised to a power, divide, multiply and perform other Operation with large numbers in mind. I on myself was convinced that it does not need to be a genius or have an incredible memory for numbers. Suffice it to remember patterns that lead authors, and spend a little time.

Each chapter tells about new ways of calculating:

1. Simple calculations in mind.
2. Verbal addition and subtraction of large numbers.
3. approximate estimate skill.
4. Memorable numbers.

How to instantly multiply any number by 11

One of the easiest methods. In order to multiply any two digit number by 11, to lay down enough two extreme figures and the amount of supply between them.

Example: 45 × 11.

4 + 5 = 9, 9 set between 4 and 5, and receive a response 495.

With the three-digit number is only slightly more complicated.

Example: 416 × 11.

Recent figures remain in place, that is, the answer is 4 ** 6. In order to find the two missing numbers need to add the first number to the second and second to third. 4 + 1 = 5; 1 + 6 = 7. Answer: 4576.

Squaring the three-digit numbers

This rather complex problem easily solved by using a simple template.

For the construction of three-digit number in the square it should be rounded up or down to produce 100 times.

That is, to find 193 ^ 2, you need to divided his two numbers. Imagine that one number is at the top, and the second at the bottom. Upper need to round to 200, adding 7, the lower the number you need to subtract the same number, which we added to the top and get 186. Now you need to multiply 2 by 186 and add two zeros, and then add to get the number of the square of the number that we took away and added, that is, 7 ^ 2 = 49.

Example: 193^2.

1. Rounding up to 100 times and subtract the same number (7) to give two numbers - 200 and 186.
2. Multiply them by getting 37200 (2 × 186 = 372 and add the two zero).
3. We add the square of the number of the first step (7 ^ 2 = 49) and obtain 37,249.

It looks a bit confusing, but the authors turned to convey the idea much easier, but after a couple of solved examples of these actions have already been made on the machine.

Rule of thumb

To memorize the numbers from 0 to 5 is sufficient to bend the right amount of fingers on a hand. Here's what to do if you want to remember more numbers:

• 6 - Place your thumb on top of the little finger;
• 7 - on top of the nameless;
• 8 - above the average;
• 9 - on top of the index.

Accordingly, using two hands, you will be able to store twice as many numbers or use one hand to remember the hundreds, and the second to memorize dozens.

Some interesting calculations

Rule 70: to find the number of years required to double your money, you need to divide the number 70 on the annual interest rate. For example, if the annual interest rate - 5%, then 70: 5 = 14 - 14 years old will need to double the amount.

Rule 110: to find the number of years required for a tripling of money, you need to divide the number 110 on the annual interest bet.

Output

"Magic numbers" - incredibly useful book for anyone who has to deal with a large number of calculations, or for those who want to impress your friends with instant calculations of three-, four- and five-digit numbers. In the book, a huge number of practical problems, and at the end of each chapter there are examples of solutions. With the correct answers can be found in the book.

The book has left a very good impression. This is one of those books, which is so much useful information that you just do not have time to digest it. This book should always be at hand to refresh your memory, or to strain the brain, solving complex problems in mind.

"Magic numbers" Arthur Benjamin, Michael Shermer

Buy litersBuy at amazon