Tips Mental Arithmetic You Can't Find in Textbooks

Learn fast math rules that you can't find in textbooks or school chairs. This article explains the key facts and context behind mental arithmetic.

Have you ever been bored with complicated calculations, tough problems that have to be dealt with on a daily basis? If the answer is yes, don't worry.

Here is a collection of quick calculation methods, extremely interesting mathematical rules, easy to apply in life, and arousing the inspiration of mathematical discovery in each of us.

• The way to teach children fast mental arithmetic of Japanese people.
• Quick and accurate mental math tips that surprise you.

Russian multiplication

One of the common methods to perform multiplication between numbers between 6 and 10 without the multiplication table is: "Russian multiplication".

Accordingly, you only need to number two hands from 6 to 10 as shown in the figure. Then snap two fingers corresponding to the multiplication to be performed (eg 7 x 8).

Then, take the total number of fingers below the two fingers multiplying by 10, bring the result plus the number of fingers above that we get the result to look for.

Quickly calculate with a two-digit number with the end of 5.

To quickly calculate the square of any two-digit number that ends in 5, use the following trick: get the tens digit multiplied by that number plus 1, get the result, then write 25 more then we get the right result.

A typical example is the square of 95: 95 ^ 2 = 9 x (9 + 1) & 25 = 9025.

Pi = PIE (pie)

Pi is a great invention in mathematics, but not everyone remembers its true value. At a simple level, just remember that Pi = PIE (the cake) then reverse the letters of this word will be 3.14 - the usual value of Pi number.

More complex, to remember longer decimal numbers of Pi numbers, learn this sentence "May I have a large container of coffee?" then count the number of letters of each word, we will get 3.1415926.