First of all, we should know the calculation method of carry addition, whether it is two digits plus one digit or two digits, its most basic principle is addition principle within 20. The quick calculation formula is: add 9, enter 1, and subtract1;
1 plus 8 MINUS 2; A few plus seven; Enter 1 minus 3, and so on. For addition within 100, look at the two-digit number and find out the larger number in the middle, which will be quickly calculated according to the formula.
In addition and subtraction in mathematics, the method of adding ten can achieve the purpose of fast calculation. Such as19,28. In the multiplication and division method, you can also calculate quickly and skillfully, or you can add up to ten, hundred and thousand, which makes the calculation simple and easy. Like 2? 5= 10,4? 25= 100,8? 125= 1000。
The fast calculation method of multiplication and division is as follows:
When adding and subtracting, "measure the part in brackets first, then measure it from left to right" is the basic algorithm. Rounding method is the most commonly used clever calculation method, that is, when calculating, priority is given to the parts that can get whole ten, whole hundred and whole thousand, so as to achieve the purpose of clever calculation.
If you want to round up ten numbers, you should get 0 at the end of the two numbers. In this case, besides 00, there are 19, 28, 37, 46, 55.
Pay special attention to the digits of each addend when doing the problem, and see if you can find a suitable solution. Addition and subtraction can be rounded up, and addition and subtraction can also be rounded up. After subtracting two numbers with the same number of digits, you can get an integer of ten.
Decomposition addition and subtraction: In addition and subtraction of fractions, a fraction is divided into two fractions for difference or addition, which makes the implied arrangement and combination clear, offsets some of the achievements, and usually greatly simplifies the calculation.
Ten digits with the same digit and different types of two-digit multiplication multiplicand plus the number of investment multipliers, and then multiplied by the integer amount of ten digits, the product is the front product.
Multiply one digit by one digit, and add up to the product. The first number is the same. The sum of the last two digits and the two digits equivalent to 10 is multiplied by the ten digits plus 1, and the sum is multiplied by the ten digits. The number is the front product, and the single digits are multiplied. The number is the back product, and there is no ten digits to make up 0.
Increase and decrease difference method: the difference between the previous addend and the last addend is equal to the sum. Subtraction plus difference method: Subtract subtree from the integer of subtree and add the difference between subtree and integer, which equals the difference.