Math Story of Grade Two 1: The origin of Arabic numerals Xiaoming is a child who likes to ask questions. One day, he became interested in the numbers 0-9: Why are they called Arabic numerals?
So he asked his mother who was a math teacher: Since 0-9 is called Arabic numerals, it must have been invented by Arabs, right, mom?
Mom shook her head and said that Arabic numerals were actually invented by Indians. About 1500 years ago, Indians used a special word to represent numbers. There are 10 words, and you can write both strokes. Later, due to contacts between countries, these figures were introduced into Arabia. Arabs thought they were very simple, so they began to use them widely in their own countries and spread throughout Europe. In this way, they gradually became the numbers we use today. Because Arabs have played a great role in spreading such numbers, people are used to calling them Arabic numbers.
Xiao Ming said happily, I see. Mom, can this be called turning mistakes into mistakes? Xiao Ming and his mother both laughed.
Math Story 2 of Grade Two: Calculator of Your Body Our body is really wonderful, and the hand is an ordinary calculator. The most common hand is the multiple calculation of 9. Parents may not understand, but many children will soon learn. When calculating the multiple of 9, put your hands on your knees and count your fingers from left to right, as shown in the table below. Now choose the multiple of 9 you want to calculate. Suppose this multiplication is 7? 9。 As shown in the above picture, just bend the finger marked with the number 7. Then count the left index finger of the bent finger as 6, and the index of the left hand on its right is 3. Put them together and get 7? The answer to 9 is 63.
Thales saw that people were reading the notice, so he went to check it. The initial notice said that Pharaoh wanted the smartest person in the world to measure the height of the pyramid. So I went to Pharaoh.
Pharaoh asked Thales what tools he used to measure the pyramids. Thales said he only used a stick and a ruler. He put the stick next to the pyramid. When the shadow of the stick was as long as the stick, he measured the length of the shadow of the pyramid and half the length of the bottom of the pyramid. Add these two lengths to get the height of the pyramid. Thales is really the smartest man in the world. He can easily measure the height of the pyramid without climbing to the top.
During the Warring States Period, Qi Weiwang and General Tian Ji raced horses, and Qi Weiwang and Tian Ji each had three good horses: mounted, won and dismounted. The race is divided into three times, and thousands of dollars are bet on each horse race. Because the horsepower of the two horses is almost the same, and Qi Weiwang's horse is better than Tian Ji's, most people think that Tian Ji will lose.
However, Tian Ji took the advice of his disciple Sun Bin (a famous strategist) and dismounted Qi Weiwang's horse, Ma Zhong of Qi Weiwang and Qi Weiwang. As a result, Tian Ji beat Qi Weiwang 2-/kloc-0-and won a lot of money. This is an example of China's ancient substitution game theory to solve problems.
The animal school held a children's song competition, with the elephant teacher as the referee.
The little monkey raised his hand first and began to recite: I can calculate carry addition, and the digits can only be added if they are aligned. The number of digits should be aligned with the number of digits. When the number of digits exceeds ten, the number of digits should be advanced to ten. Ten digits plus one plus one can count quickly and accurately. ?
As soon as the little monkey finished speaking, the puppy began to recite: abdication and subtraction are not difficult, and subtraction can be done if the numbers are aligned. If the single digits are small enough, ten people can borrow one. If ten people return, one will be ten, and if they return, one will be missing. How to reduce ten digits, ten digits will be reduced again and again. ?
Everyone applauded their wonderful performance. The elephant teacher said:? Their children's songs make us understand that both carry addition and abdication subtraction should win the championship, so please agree and applaud them.