乘除法速算方法
Multiplication and division arithmetic
You can go to the bookstore to buy the book to see quick ah
For example: 11 x 12=132, and the result is this: take the number 11 to "1" and "1"",
12 two numbers, namely 1+2=3 (as intermediate number) due to the end of the 11 * 12 is 2, so that the end is 2, the three numbers together is 132..
Like 11 x 13=143, 11 x 15=165, 11 x 17=187..
These books must have some knowledge about the course, based on the book but also often see children doing mental arithmetic
Article [1]; the calculation of multiplication and division,
[thematic points]
The basic ideas and the addition and subtraction multiplication and division calculation simplified, are "rounding up". According to the characteristics of the number of questions, we can calculate the number of points that can be gathered together by using the law of operation and the nature of multiplication and division.
Several special methods of calculation are as follows:
1, "the head with the tail folded" simple calculation method;
with ten multiplied by the number of ten the number 1 product as the first two digits, with a number multiplied as the last two digits (if the product is less than ten, ten to write 0).
2, the "tail head folded" simple calculation methods: Ten bit digital product plus a digit and then multiplied by 100, finally a product of digital product.
3, two digits, three digits multiplied by 11: (1) the head of the head of the plot; (2) the tail of the end of the product; (3, the head and tail addition (or the first two digits of the three digits and the sum of the two digits) as the middle of the product. If 10 (100) goes forward, 1".
Example 1. Simple calculation of the following questions
(1) 4 x 8 x 25 * 125
(2) (400125) * 8
= (4 * 25) * (8 * 125)
(using the distributive law of multiplication)
= 100 * 1000
,×,×8 125 8 400
,100000
,3200×1000
遇到因数5，找个因数2
,2200
遇到因数25，找个因数4
遇到因数125，找个因数8
(3)8 64 61 8×，×
(4)98×101
(利用乘法分配律)
(利用乘法分配律)
,8×(64，61)
,98×(100，1)
,8×125
,×，×1 98 100 98
,1000
,9800，98
,9898
2、计算下面个
题
快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题
例题
(1)425?25
(2)7900 25 4??
,(425×4)?(25，4)
,7900?(25×4)
,1700?100
,7900?100
,17
,79
两个数相除，它们同时扩大或缩
一个连续除以这几个数，等
小相同的倍数，商不变。
于这个除以这几个数的积。
(扩大或缩小的数是不能是0。)
一个?B?C,一?(B×C)
一个?B C D??,一?(B C D××)
(3)(255，170)?17
(4)1950 13 5??
,?，?17 170 17 255
,??1950 5 13
,15，10
,390?13
,25
,30
除法分配律(乘法分配的拓展应用)，也叫陈氏定律。
被除数是几个数的和或差，除数只有1个，就可以用除法分配。
就是把被除数的每个数分别去除除数，再加或减。
运算符号搬家:
54 12 47 54×，×，54×41
628×51-628
,54×(12，47，41)
,×,×1 628 51 628
,54×100
,628×50
,5400
3、计算例题
(1)63×67(2)399×11
(3)27×87
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