Method 1. Two-digit carry addition: formula: add 9 minus 1, add 8 minus 2, add 7 minus 3, add 6 minus 4, add 5 minus 5, add 4 minus 6, add 3 minus 7, add 2 minus 8, add/kloc-0 minus 9 (Note: 6 minus 2.38 on 26, and 3 in the tenth place should be carried to 4. (Note: How to carry the tenth digit in the last two digits is 1, I enter 2, 2, 3, 4, and so on. Where should I carry it? If this is 3, I enter 4, and the first two digits are 2+4. If three into four plus two equals six, write with ten digits. Another example is that 42+29=7 1. Just use the sentence "plus 9 minus 1", 2- 1= 1, write 1 with one digit, which means 2, and I will enter 3,4+3 = 7. Faster than a calculator. If you add two digits and don't add two digits, you can write the numbers directly, for example, 25+34=59. Write one digit plus one digit on the number after the equal sign, 5+4=9, and write ten digits plus ten digits on the ten digits, so 2+3=5, which is 59. No vertical calculation is required.

Method two. Subtract the abdication of two digits. Oral formula: minus 9 plus 1, minus 8 plus 2, minus 7 plus 3, minus 6 plus 4, minus 5 plus 5, minus 4 plus 6, minus 3 plus 7, minus 2 plus 8, minus 1 plus 9. (Note:

Subtracting a few words from oral judgment means subtracting a number from a place. For example: 73-46=27. If you subtract 6, you will add 4. Who will add 4? Three plus four equals seven. Written in one place, the decimal place of subtraction is four. I will retire. Who will retire? Seven to five, that's 27. (Note: How to abdicate? The decimal place of subtraction is 1, you retreat 2, if 2, you retreat 3, if 3, you retreat 4, and so on. However, this retreat can only be carried out if the single digit is not reduced enough. If you subtract enough, you can directly subtract one digit, and subtract ten digits to directly determine the number. )