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Japanese number multiplication system. Chinese or Japanese multiplication. The best results are achieved by the one who exercises regularly at home.























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"Counting and computing is the basis of order in the head."
Pestalozzi

Target:

  • Get acquainted with the old methods of multiplication.
  • Expand knowledge of various multiplication techniques.
  • Learn to perform actions with natural numbers using the old methods of multiplication.
  1. The old way to multiply by 9 on your fingers
  2. Ferrol multiplication.
  3. The Japanese way of multiplying.
  4. Italian way of multiplication ("Grid")
  5. Russian way of multiplication.
  6. The Indian way of multiplying.

Course of the lesson

The relevance of the use of fast counting techniques.

V modern life each person often has to perform a huge amount of calculations and calculations. Therefore, the goal of my work is to show easy, fast and accurate counting methods that will not only help you during any calculations, but will cause considerable surprise to friends and acquaintances, because the free execution of counting operations can largely testify to the outstandingness of your intellect. Conscious and robust computational skills are a foundational element of a computing culture. The problem of the formation of a computational culture is relevant for the entire school mathematics course, starting from the elementary grades, and requires not just mastering computational skills, but using them in various situations. Possession of computational skills and abilities has great importance to assimilate the material under study, it allows you to cultivate valuable labor qualities: a responsible attitude to your work, the ability to detect and correct mistakes made in work, accurate execution of tasks, a creative attitude to work. However, in recent years, the level of computing skills, transformations of expressions has a pronounced tendency to decrease, students make a lot of mistakes in calculations, more and more often use a calculator, do not think rationally, which negatively affects the quality of teaching and the level of mathematical knowledge of students in general. One of the components of the computing culture is verbal counting which is of great importance. The ability to quickly and correctly make simple calculations “in the mind” is necessary for every person.

Old ways of multiplying numbers.

1. The old way of multiplying by 9 on your fingers

It's simple. To multiply any number from 1 to 9 by 9, look at your hands. Bend the finger that corresponds to the number to be multiplied (for example, 9 x 3 - bend the third finger), count the fingers to the curled finger (in the case of 9 x 3, this is 2), then count after the curled finger (in our case, 7). The answer is 27.

2. Multiplication by Ferrol's method.

To multiply the units of the multiplication product, multiply the units of the multipliers, to get tens, multiply tens of one by units of the other and vice versa and add the results, to get hundreds, multiply tens. Using Ferrol's method, it is easy to orally multiply two-digit numbers from 10 to 20.

For example: 12x14 = 168

a) 2x4 = 8, write 8

b) 1x4 + 2x1 = 6, write 6

c) 1x1 = 1, we write 1.

3. Japanese way of multiplication

This technique resembles multiplication by a column, but it takes quite a long time.

Using the technique. Let's say we need to multiply 13 by 24. Let's draw the following figure:

This drawing consists of 10 lines (the number can be any)

  • These lines represent the number 24 (2 lines, indent, 4 lines)
  • And these lines represent the number 13 (1 line, indent, 3 lines)

(intersections in the figure are indicated by dots)

Number of intersections:

  • Top left edge: 2
  • Bottom left edge: 6
  • Top right: 4
  • Bottom Right: 12

1) Intersections at the top left edge (2) - the first number of the answer

2) The sum of the intersections of the lower left and upper right edges (6 + 4) - the second number of the answer

3) Intersections at the bottom right edge (12) - the third number of the answer.

It turns out: 2; 10; 12.

Because the last two numbers are two-digit and we cannot write them down, then we write down only ones, and add tens to the previous one.

4. The Italian way of multiplication ("Grid")

In Italy, as well as in many countries of the East, this method has gained great popularity.

Using the trick:

For example, let's multiply 6827 by 345.

1. Draw a square grid and write one of the numbers above the columns, and the second in height.

2. Multiply the number of each row sequentially by the numbers of each column.

  • 6 * 3 = 18. Write down 1 and 8
  • 8 * 3 = 24. Write 2 and 4

If the multiplication results in a single-digit number, write 0 at the top, and this number at the bottom.

(As in our example, when multiplying 2 by 3, we got 6. At the top we wrote 0, and at the bottom 6)

3. Fill in the entire grid and add the numbers following the diagonal stripes. We start folding from right to left. If the sum of one diagonal contains tens, then we add them to the units of the next diagonal.

Answer: 2355315.

5. Russian way of multiplication.

This multiplication technique was used by Russian peasants about 2-4 centuries ago, and was developed in ancient times. The essence of this method is: “By how much we divide the first factor, we multiply the second by so much.” Here is an example: We need to multiply 32 by 13. This is how our ancestors would have solved this example 3-4 centuries ago:

  • 32 * 13 (32 is divided by 2, and 13 is multiplied by 2)
  • 16 * 26 (16 is divided by 2, and 26 is multiplied by 2)
  • 8 * 52 (etc.)
  • 4 * 104
  • 2 * 208
  • 1 * 416 =416

The division in half is continued until the quotient is 1, while doubling another number in parallel. The last doubled number gives the desired result. It is not difficult to understand what this method is based on: the product does not change if one factor is halved and the other is doubled. It is therefore clear that as a result of repeated repetition of this operation, the desired product is obtained

However, what should you do if you have to halve an odd number? The popular method easily gets out of this difficulty. It is necessary, - the rule says, - in the case of an odd number, discard one and divide the remainder in half; but on the other hand, to the last number of the right column, it will be necessary to add all those numbers of this column that stand against the odd numbers of the left column: the sum will be the desired product. In practice, this is done so that all lines with even left numbers are crossed out; only those remain that contain an odd number to the left. Here's an example (asterisks indicate that this line should be crossed out):

  • 19*17
  • 4 *68*
  • 2 *136*
  • 1 *272

Adding the uncrossed numbers, we get a completely correct result:

  • 17 + 34 + 272 = 323.

Answer: 323.

6. The Indian method of multiplication.

This method of multiplication was used in ancient India.

To multiply, for example, 793 by 92, we write one number as a multiplier and under it another as a multiplier. For easier orientation, you can use the grid (A) as a reference.

Now we multiply the left digit of the multiplier by each digit of the multiplier, that is, 9x7, 9x9 and 9x3. We write the resulting works in the grid (B), keeping in mind the following rules:

  • Rule 1. The units of the first product should be written in the same column as the multiplier, that is, in this case, under 9.
  • Rule 2. Subsequent works should be written in such a way that the units fit in the column immediately to the right of the previous work.

Let's repeat the whole process with other multiplier digits, following the same rules (C).

Then we add the numbers in the columns and get the answer: 72956.

As you can see, we get a large list of works. The Indians, who had a lot of practice, wrote each number not in the corresponding column, but at the top, as far as possible. Then they added the numbers in the columns and got the result.

Conclusion

We have entered the new millennium! Great discoveries and achievements of mankind. We know a lot, we can do a lot. It seems something supernatural that with the help of numbers and formulas one can calculate the flight of a spaceship, the “economic situation” in the country, the weather for “tomorrow”, and describe the sound of notes in a melody. We know the statement of the ancient Greek mathematician, philosopher who lived in the 4th century BC - Pythagoras - “Everything is number!”.

According to the philosophical view of this scientist and his followers, numbers control not only measure and weight, but also all phenomena occurring in nature, and are the essence of harmony that reigns in the world, the soul of the cosmos.

Describing the old ways of computing and modern methods of fast counting, I tried to show that, both in the past and in the future, one cannot do without mathematics, a science created by the human mind.

“Those who have been engaged in mathematics since childhood develops attention, trains the brain, their will, fosters perseverance and perseverance in achieving the goal.”(A. Markushevich)

Literature.

  1. Encyclopedia for children. “T.23”. Universal encyclopedic dictionary \ ed. Collegium: M. Aksyonova, E. Zhuravleva, D. Lury and others - M .: World of Encyclopedias Avanta +, Astrel, 2008. - 688 p.
  2. Ozhegov S. I. Dictionary of the Russian language: apprx. 57,000 words / Ed. member - corr. ANSIR N.Yu. Shvedova. - 20th ed. - M.: Education, 2000. - 1012 p.
  3. I want to know everything! Great Illustrated Encyclopedia of Intellect / Per. from English A. Zykova, K. Malkova, O. Ozerova. - Moscow: EKMO Publishing House, 2006 .-- 440 p.
  4. Sheinina O.S., Solovieva G.M. Maths. Classes of a school circle 5-6 grades / O.S. Sheinina, G.M. Solovyov - Moscow: NTsENAS Publishing House, 2007 .-- 208 p.
  5. Kordemsky B.A., Akhadov A.A.
  6. Minskikh EM “From game to knowledge”, M., “Enlightenment” 1982
  7. Svechnikov A.A.Numbers, figures, problems M., Enlightenment, 1977.
  8. http: // matsievsky. newmail. ru / sys-schi / file15.htm
  9. http: //sch69.narod. ru / mod / 1/6506 / hystory. html

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In Russia, we are used to multiplying numbers in the traditional way that we were taught in school, writing down the multiplier numbers in a column (). However, in Asian countries such as Japan and China, it is considered differently. For a contemplative oriental mentality, an indispensable visualization is important. Even the Arabic numerals generally recognized in the world are written by the Chinese and Japanese in hieroglyphs. It is with the peculiarity of the Asian graphic system that the Japanese and Chinese method of multiplying numbers is associated.

This video shows you how to multiply in Japanese and Chinese:

It will seem to many that this method of Japanese or Chinese multiplication is too complicated and confusing, but this is only at first glance. It is visualization, that is, the image of all points of intersection of straight lines (multipliers) on one plane, that gives us visual support, while the traditional method of multiplication involves a large number of arithmetic operations only in the mind. Chinese or Japanese multiplication helps not only to quickly and efficiently multiply two-digit and three-digit numbers by each other without a calculator, but also develops erudition. Agree, not everyone can boast that in practice they know the ancient Chinese method of multiplication (*), which is relevant and works great in the modern world.

*) Japanese or Chinese multiplication table? Archaeologists in Japan have found a wooden tablet with a fragment of the multiplication table, which was supposedly made in the 8th century. Scientists believe that such tables were used by Japanese imperial officials, who needed to master various sciences, including arithmetic.
The discovered tablet is the oldest of all previously found in Japan. Interestingly, the hieroglyphs used to write the numbers are very similar in style to those that were used as an official letter during the Chinese Tang dynasty of the 7th-10th centuries. Based on this, the scientists assumed that the table was copied from the Chinese arithmetic textbook of that time, that is, the entire Japanese multiplication table was borrowed from China.

It was to their neighbors in China that high-ranking Japanese went every year to learn from them different sciences, such as arithmetic. The ancient Chinese multiplication table was not an easy one, as it involved multiplying two-digit numbers by each other. It is unlikely that all Japanese officials could learn such a table by heart, therefore they carried with them to work something like a cheat sheet, a fragment of one of which is a tablet found by archaeologists in Japan.

So, the Japanese multiplication table was borrowed from the Chinese, who, according to some hypotheses, were among the creators of the first arithmetic system, as evidenced by archaeological finds containing fragments of the multiplication table, the age of which scientists have estimated at 2700-3000 years.

What is mental arithmetic and why every person needs it.

Mental arithmetic is a program for the integrated development of the intellect and thinking of children, based on the formation of the skill of quick verbal counting

In the classroom, children learn quick counting using a special counting board (abacus, soroban). Teachers explain how to correctly sort the knuckles on the knitting needles so that kids can almost instantly get an answer to complex example... Gradually, the attachment to the accounts weakens and the children imagine the actions that they performed with the accounts in their minds.

The program is designed for 2-2.5 years. First, the guys master addition and subtraction, then multiplication and division. A skill is acquired and developed through repeated repetition of the same actions. The methodology is suitable for almost all children, the teaching principle is from simple to complex.

Classes are held once or twice a week and last one to two hours.

The ancient abacus abacus, on which children count, have been known for more than 2.5 thousand years.

In Japan, abacus counting is included in the official school curriculum.

For more than 50 years, mental arithmetic has been part of the public education system in Japan. Interestingly, after graduation, people continue to improve their oral counting skills. In the Land of the Rising Sun, mental arithmetic is considered a kind of sport. They even hold competitions on it. In Russia, international tournaments in Mental Arithmetic are now also held annually.

Mental arithmetic develops mechanical and photographic memory

When children count, they use both hemispheres of the brain at once. Mental arithmetic develops photographic and mechanical memory, imagination, observation, improves concentration.

The general level of intelligence rises. This means that it is easier for children to assimilate large amounts of information in a short time. Success in foreign languages... It is no longer necessary to spend the whole day memorizing poetry and prose.

Slower schoolchildren have a faster reaction rate. They begin not only to count at lightning speed, but to think faster and make decisions not related to arithmetic.

There are also unexpected results. One day a boy who played tennis came to the center. The mother said that her son had problems with coordination of movements. Unexpectedly, it was possible to solve them precisely at the expense of intensives in mental arithmetic.

Mental arithmetic is more difficult for adults, the optimal age for starting classes is 5-14 years

It is possible to develop the brain with the help of mental arithmetic at any age, but the best results can be achieved before the age of 12-14. Children's brain is very flexible and mobile. At a young age, neural connections are most actively formed in it, so our program is easier for children under 14 years old.

The older a person is, the more difficult it is for him to abstract from his experience and knowledge and simply trust the abacus. I mastered this technique at the age of 45 and constantly doubted whether I was getting it right, whether there was no mistake. This greatly interferes with learning.

But what harder to man master this account, the more benefit from it. A person, as it were, overcomes himself, each time he gets better and better. Classes are not in vain, the brain of an adult is also actively developing.

Just do not expect the same results from an adult as from a child. We can learn the technique, but we won't be able to count as quickly as a second grader does. Experience shows that the optimal age from which it is better to start classes is 6 and 7 years.

The best results are achieved by the one who exercises regularly at home.

A prerequisite for training is daily abacus training. Just 10-15 minutes. Children need to work out the formula that the teacher gave them in the lesson, and bring their actions to automatism. Only in this case will the child learn to count quickly. The organizational role of parents is important here, who need to monitor regular exercise.

Children do not get tired in the classroom due to the constant change of activities

The main activity in mental arithmetic is counting on the abacus. Children count in different ways: by ear, in workbooks, at the blackboard on a demonstration abacus, using the Cheerful Soroban electronic simulator, on a mental map (this is a graphic image of an abacus, with the help of which children imagine how the bones are moved on the abacus).

Image copyright Getty Images Image caption I wouldn't get a headache ...

"Mathematics is so difficult ..." You have probably heard this phrase more than once, and perhaps even pronounced it aloud yourself.

For many, mathematical calculations are not easy, but here are three easy ways to help you complete at least one arithmetic operation- multiplication. No calculator.

It is likely that at school you got acquainted with the most traditional way of multiplication: first you learned the multiplication table by memory, and only then you began to multiply each of the digits in a column, which are used to write multi-digit numbers.

If you need to multiply multi-digit numbers, then finding the answer will take a large sheet of paper.

But if this long set of lines with numbers going one under the other makes your head spin, then there are other, more visual methods that can help you in this matter.

But there are some artistic skills that come in handy.

Let's draw!

At least three methods of multiplication involve drawing intersecting lines.

1. Mayan way, or Japanese method

There are several versions regarding the origin of this method.


Is it hard to multiply in your mind? Try the Maya and Japanese method

Some say that it was invented by the Mayan Indians who inhabited areas of Central America before the arrival of the conquistadors in the 16th century. It is also known as the Japanese multiplication method, as teachers in Japan use this visual method when teaching. junior schoolchildren multiplication.

The bottom line is that parallel and perpendicular lines represent the digits of those numbers that need to be multiplied.

Let's multiply 23 by 41.

To do this, we need to draw two parallel lines representing 2, and, backing slightly, three more lines representing 3.

Then, perpendicular to these lines, we will draw four parallel lines representing 4 and, slightly indented, another line for 1.

Well, is it really difficult?

2. Indian way, or Italian multiplication by "lattice" - "gelosia"

The origin of this multiplication method is also not clear, but it is well known throughout Asia.

"The" Gelosia "algorithm was transmitted from India to China, then to Arabia, and from there to Italy in the XIV-XV centuries, where it was called" Gelosia ", because it looked like Venetian latticed shutters," writes Mario Roberto Canales Villanueva in his book on different ways of multiplying.

Image copyright Getty Images Image caption Indian or Italian multiplication system is similar to Venetian blinds

Let's take the example of multiplying 23 by 41 again.

Now we need to draw a table of four cells - one cell per digit. Let's sign the corresponding number on top of each cell - 2,3,4,1.

Then you need to divide each cell in two diagonally to get triangles.

Now we first multiply the first digits of each number, that is, 2 by 4, and write 0 in the first triangle, and 8 in the second.

Then we multiply 3x4 and write 1 in the first triangle and 2 in the second.

Let's do the same with the other two numbers.

When all the cells of our table are filled in, we add the numbers in the sequence shown in the video and write down the resulting result.


Media playback is unsupported on your device

Is it hard to multiply in your mind? Try the Indian method

The first digit will be 0, the second is 9, the third is 4, and the fourth is 3. Thus, the result is 943.

Do you think this method is easier or not?

Let's try another multiplication method using a picture.

3. "Array", or table method

As in the previous case, this will require drawing a table.

Let's take the same example: 23 x 41.

Here we need to divide our numbers into tens and ones, so we will write 23 as 20 in one column, and 3 in the other.

Vertically, we write 40 at the top, and 1 at the bottom.

Then we will multiply the numbers horizontally and vertically.


Media playback is unsupported on your device

Is it hard to multiply in your mind? Draw a table.

But instead of multiplying 20 by 40, we discard the zeros and simply multiply 2 x 4 to get 8.

Do the same by multiplying 3 by 40. We hold 0 in parentheses and multiply 3 by 4 to get 12.

Let's do the same with the bottom row.

Now let's add zeros: in the upper left cell we got 8, but we dropped two zeros - now we add them and we get 800.

In the upper right cell, when we multiplied 3 by 4 (0), we got 12; now we add zero to get 120.

Let's do the same for all other held zeros.

Finally, we add up all four numbers obtained by multiplying in the table.

Result? 943. Well, how did it help?

Variety is important

Image copyright Getty Images Image caption All methods are good, the main thing is that the answer converges

What can be said for sure is that all these different methods gave us the same result!

We still had to multiply a few things in the process, but each step was easier than when multiplying in the traditional way, and much more intuitive.

So why is it that few places in the world in mainstream schools teach these calculation methods?

One of the reasons may be the emphasis on teaching "mental calculations" - to develop mental abilities.

However, David Weese, a Canadian mathematics teacher working in public schools in New York, explains it differently.

"I recently read that the reason the traditional multiplication method is used is to save paper and ink. This method was not thought to be the easiest to use, but the most economical in terms of resources, as ink and paper were in short supply." Wiz explains.

Image copyright Getty Images Image caption For some calculation methods, only the head is not enough, you also need felt-tip pens

Despite this, he believes that alternative multiplication methods are very useful.

“I don’t think it’s useful to immediately teach schoolchildren to multiply, forcing them to learn the multiplication table, but without explaining to them where it came from. Because if they forget one number, how can they advance in solving the problem? the Japanese method is necessary because with it you can understand general structure multiplication, which is a good start, "says Wiz.

There are a number of other methods of multiplication, for example, Russian or Egyptian, they do not require additional drawing skills.

According to the experts with whom we spoke, all these methods help to better understand the process of multiplication.

“It’s clear that everything is good. Mathematics in today's world is open both inside and outside the classroom,” sums up Andrea Vasquez, a math teacher from Argentina.

published 20.04.2012
Dedicated to Elena Petrovna Karinskaya ,
my school math teacher and class teacher
Almaty, ROFMSh, 1984-1987

"Science only achieves perfection when it manages to use mathematics"... Karl Heinrich Marx
these words were inscribed above the blackboard in our math classroom ;-)
Informatics lessons(lecture materials and workshops)


What is multiplication?
This is an addition action.
But not too pleasant
Because many times ...
Tim Sobakin

Let's try to do this action
pleasant and exciting ;-)

METHODS OF MULTIPLICATION WITHOUT MULTIPLICATION TABLE (gymnastics for the mind)

I offer the readers of the green pages two methods of multiplication, which do not use the multiplication table ;-) I hope that this material will appeal to teachers of computer science, which they can use when conducting extracurricular activities.

This method was used in the everyday life of Russian peasants and inherited by them from ancient times. Its essence is that the multiplication of any two numbers is reduced to a series of consecutive divisions of one number in half while doubling another number, multiplication table in this case unnecessarily :-)

The division in half is continued until the quotient is 1, while another number is doubled in parallel. The last doubled number gives the desired result(picture 1). It is not difficult to understand what this method is based on: the product does not change if one factor is halved and the other is doubled. It is therefore clear that as a result of repeated repetition of this operation, the desired product is obtained.


However, what to do if you have to halve an odd number? In this case, we discard one from the odd number and divide the remainder in half, while all those numbers of this column that are opposite the odd numbers of the left column will need to be added to the last number of the right column - the sum will be the desired product (Figures: 2, 3).
In other words, cross out all lines with even left numbers; leave and then summarize not strikethrough numbers right column.

For Figure 2: 192 + 48 + 12 = 252
The correctness of the reception will become clear if you take into account that:
5 × 48 = (4 + 1) × 48 = 4 × 48 + 48
21 × 12 = (20 + 1) × 12 = 20 × 12 + 12
It is clear that the numbers 48 , 12 , lost when dividing an odd number in half, must be added to the result of the last multiplication to get the product.
The Russian way of multiplication is both elegant and extravagant at the same time ;-)

§ Logic puzzle about Serpent Gorynyche and famous Russian heroes on the green page "Which of the heroes defeated the Serpent Gorynych?"
solution logical tasks logic algebra
For those who love to learn! For those who are happy gymnastics for the mind ;-)
§ Solving logical problems in a tabular way

We continue the conversation :-)

Chinese??? The drawing way of multiplication

My son introduced me to this method of multiplication, having provided me with several pieces of paper from a notebook with ready-made solutions in the form of intricate drawings. The process of decrypting the algorithm has begun to boil pictorial way of multiplication :-) For clarity, I decided to resort to the help of colored pencils, and ... gentlemen of the jury broke the ice :-)
I bring to your attention three examples in color pictures (in the upper right corner check post).

Example # 1: 12 × 321 = 3852
Draw first number top to bottom, left to right: one green stick ( 1 ); two orange sticks ( 2 ). 12 drew :-)
Draw second number from bottom to top, from left to right: three blue sticks ( 3 ); two reds ( 2 ); one lilac ( 1 ). 321 drew :-)

Now we will walk through the drawing with a simple pencil, divide the points of intersection of the numbers-sticks into parts and start counting the points. Moving from right to left (clockwise): 2 , 5 , 8 , 3 . Result number we will "collect" from left to right (counterclockwise) and ... voila, we got 3852 :-)


Example # 2: 24 × 34 = 816
There are some nuances in this example ;-) When counting the points in the first part, it turned out 16 ... We send one-add to the dots of the second part ( 20 + 1 )…


Example # 3: 215 × 741 = 159315
No comments:-)


At first it seemed to me somewhat pretentious, but at the same time intriguing and surprisingly harmonious. On the fifth example, I caught myself thinking that multiplication goes into flight :-) and works in autopilot mode: draw, count points, we don't remember the multiplication table, it seems like we don't know it at all :-)))

To be honest, by checking drawing way of multiplication and turning to multiplication by a column, and more than once, not twice, to my shame, I noted some slowdowns, indicating that my multiplication table rusted in some places :-( and you shouldn't forget it. When working with more "serious" numbers drawing way of multiplication became too cumbersome, and column multiplication went into joy.

Multiplication table(sketch of the back of the notebook)


P.S.: Glory and praise to the native Soviet column!
In terms of construction, the method is unpretentious and compact, very fast, memory trains - the multiplication table does not allow forgetting :-) And therefore, I strongly recommend that you and yourself and you, if possible, forget about calculators in phones and computers ;-) and periodically indulge yourself with column multiplication. Otherwise, it’s not even an hour and the plot from the movie "Rise of the Machines" will unfold not on the cinema screen, but in our kitchen or the lawn next to our house ...
Three times over the left shoulder ... knocking on wood ... :-))) ... and most importantly do not forget about gymnastics for the mind!

For the curious: Multiplication denoted by [×] or [·]
The [×] sign was introduced by an English mathematician William Outread in 1631.
The [·] sign was introduced by a German scientist Gottfried Wilhelm Leibniz in 1698.
In the letter designation, these signs are omitted and instead of a × b or a · b write ab.

In the piggy bank of the webmaster: Some mathematical symbols in HTML

° ° or °degree
± ± or ±plus or minus
¼ ¼ or ¼fraction - one quarter
½ ½ or ½fraction - one second
¾ ¾ or ¾fraction - three quarters
× × or ×multiplication sign
÷ ÷ or ÷division sign
ƒ ƒ or ƒfunction sign
' or 'single stroke - minutes and feet
" or "double prime - seconds and inches
≈ or ≈roughly equal sign
≠ or ≠not equal
≡ or ≡identically
> > or>more
< < или smaller
≥ or ≥more or equal
≤ or ≤less than or equal to
∑ or ∑summation sign
√ or √square root (radical)
∞ or ∞Infinity
Ø Ø or Ødiameter
∠ or ∠injection
⊥ or ⊥perpendicular
 


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