(1) Two digits plus two digits

1, two-digit plus two-digit non-carry addition calculation rule: align the same numbers vertically, and then add the numbers on the same numbers.

2. The calculation rules of two-digit plus two-digit carry addition: ① the same digits are aligned; (2) from the unit; (3) exactly ten into ten equals 1.

3. When writing, add two numbers, and the same numbers should be aligned, starting with a single number. When each number is full of+,add "1" to the tenth digit. Don't leave out "1" when adding the tenth digit.

4. Total = Appendix+Appendix

One addend = and-the other addend.

(2) Two digits minus two digits

1, two-digit subtraction without abdication: the same number is vertically aligned, and then the number on the same number is subtracted.

2. Two-digit minus two-digit abdication minus written calculation rules:

(1) The same number is aligned;

(2) from the unit;

(3) If there are not enough digits, subtract 1 from one digit and 10 from one digit.

3. When writing, subtract two numbers from two numbers, and align the same numbers. Starting with single digits, single digits are not enough. Starting from the tenth digit, subtract 1, add 10 to the single digit and then subtract. When calculating ten digits, the backward 1 should be subtracted before calculation.

4. Difference = minus-minus

Negative = negative+difference

Subtraction = minuend+difference

(3) Addition and subtraction and addition and subtraction.

1, plus or minus

The writing order of addition and subtraction is the same as that of oral calculation, which is calculated from left to right in turn.

The addition calculation of 1 can be calculated step by step or written vertically. The calculation method is the same as adding two numbers. The same numbers should be aligned, starting with single digits.

② The continuous subtraction operation can be calculated step by step or written as vertical calculation. The calculation method is the same as subtracting two numbers. The same numbers should be aligned, starting with single digits.

2. Add, subtract and mix

The operation order of mixed addition and subtraction formula is the same as addition and subtraction, and the writing is concise.

Second, division.

Oral grouping

1, integer+number divided by integer ten or hundred.

(1) Calculate division and want to multiply; For example, 60÷30= () can be considered as (2)*30=60.

(2) Calculated by division in the table. Use the nature of division operation: expand or shrink the dividend and divisor by the same multiple at the same time, and the quotient remains unchanged. For example, if 200÷50 wants 20÷5=4, then 200÷50=4.

2. Estimation method of dividing two digits by two digits or three digits: Division estimation is generally to "round" the numbers in the formula that are not integer ten or hundred into integer ten or hundred, and then perform oral calculation. Note that the results are marked with √.

(b) Written division of labour

1, divisor is a two-digit pen division calculation method: divide the first two digits of the dividend by the divisor first, and if the first two digits are less than the divisor, look at the first three digits. Except for the dividend, the merchants wrote it on that. The remainder after each division operation must be less than the divisor.

2. Trial-and-error method of two-digit division in which the divisor is not an integer: If the divisor is a two-digit number close to an integer, the divisor can be regarded as the trial quotient of the integer close to it by rounding, or the divisor can be regarded as the number fifteen close to it, and then the quotient can be directly determined by multiplying one digit.