浏览网站找些资料阅读的我，应该可以说是在K 网吧？（不是K 书嘛!）
在随便读读的同时，找到了有趣的 Arithmetic Tricks
喜欢数学的人可以进去看看，有点意思哦！
如果两个数字的和数不是个位数，那么将个位数保留，加1在前头：
自乘的秘诀
（不翻译了，读英文快一些）If you need to square a 2 digit number ending in 5, you can do so very easily with this trick. Mulitply the first digit by itself + 1, and put 25 on the end. That is all!
乘与11的秘诀
乘法表乘与10很简单对不对？但是其实乘与11也同样简单。
例：52 x 11 =
方法：象想 5_2 中间有个空格，让后， 5_(5+2)_2 将两个数字的和数填入那空格的。
简简单单拿到52 x 11的答案：572.
如果两个数字的和数不是个位数，那么将个位数保留，加1在前头：
例：99 x 11 =
9_(9+9)_9
(9+1)_8_9
10_8_9
9_(9+9)_9
(9+1)_8_9
10_8_9
答案：99 x 11 = 1089 有兴趣的人可以试试，我尝试了不同的数字... It works well !
自乘的秘诀
（不翻译了，读英文快一些）If you need to square a 2 digit number ending in 5, you can do so very easily with this trick. Mulitply the first digit by itself + 1, and put 25 on the end. That is all!
例：45^2 = （4x(4+1)）&25
45^2 = 2025
轻轻松松不用按计算机就可以拿到45的自乘（Square是叫自乘没错吧！）
轻轻松松不用按计算机就可以拿到45的自乘（Square是叫自乘没错吧！）
乘与9的秘诀
小时候爸爸有教过我另个秘诀，读读这个作者教的方法，也很有意思呢！
This one is simple – to multiple any number between 1 and 9 by 9 hold both hands in front of your face – drop the finger that corresponds to the number you are multiplying (for example 9×3 – drop your third finger) – count the fingers before the dropped finger (in the case of 9×3 it is 2) then count the numbers after (in this case 7) – the answer is 27.
后记：我应该看 Programming 而不是这种（简单的）数学才对的 ... xD
小时候爸爸有教过我另个秘诀，读读这个作者教的方法，也很有意思呢！
This one is simple – to multiple any number between 1 and 9 by 9 hold both hands in front of your face – drop the finger that corresponds to the number you are multiplying (for example 9×3 – drop your third finger) – count the fingers before the dropped finger (in the case of 9×3 it is 2) then count the numbers after (in this case 7) – the answer is 27.
后记：我应该看 Programming 而不是这种（简单的）数学才对的 ... xD
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