First, let the students know what is the same digit (unit and unit; Ten and ten; Hundreds of thousands .....), and then vertically on the same digit, for example, 37+24 (the digits 7 and 4 are aligned, and the tenth digit 3 and 2 are aligned), and then add from the single digit and move forward to 1 when it reaches ten. 7+4= 1 1, write 1 for one digit and1for ten digits; On the tenth digit: 3+2=5, and then 1 is 6. The tenth bit is written as 6, so 37+24=6 1. The same is true of subtraction: the numbers on the same digit are aligned and splashed from the unit (if the number on the unit is not reduced enough, 1 must be borrowed from the previous digit. For example, on 34-27, if 4-7 is not enough, borrow 1 from ten digits. Such numbers are 14, 14-7=7. Write 7 on the digit (the tenth digit was originally 3, and 1 was borrowed, leaving 2).