Addition and subtraction (1) adds two numbers. Appendix+Appendix = and: 3+ 13= 16, where 3 and 13 are addends and the sum is 16.
Take a part from a number and find out how much is left. Subtract. Negative-negative = difference
For example, 19-6= 13, 19 is the minuend, 6 is the minuend, and the difference is 13.
(1) Memorize the numbers of addition and subtraction in the table.
(2) Understand the following rules
1, addition
(1) Add two numbers and keep the number unchanged: if one of the two added numbers increases, the other decreases, the other increases and the other decreases.
(2) When two numbers are added, one of them remains the same. If the other number changes, this number will also change, and the change of the result is as big as the change of the addend.
(3) Add the two numbers and exchange positions to get the same number.
Step 2 subtract
(1) Subtract one number from another to keep the reduction unchanged: if the minuend increases, the result will also increase, and the result will increase as much as the minuend increases; When the minuend is reduced, the result is also reduced, and the result is also reduced by how much the minuend is.
(2) Subtract one number from another to keep the minuend unchanged: the meiosis increases, the result decreases, and the meiosis increases and the result decreases; If meiosis decreases, the results increase, and the results increase by how much meiosis decreases.
(3) When one number is subtracted from another, the number remains the same: the minuend increases as much as it increases; As much as the minuend is reduced, the minuend will also be reduced.
Addition and subtraction (2)
(1) Master the calculation method of carry addition within 20-"Rounding up to ten" and "Rounding up to decimal and dividing by large number", and then add up the decimal to 10 before calculation.
For example: 3+9(3+7= 10, 9 can be divided into 7 and 2, 10+2 = 12).
"Round up a large number and divide it into decimals", make a large number 10, and then calculate.
For example: 8+7(8+2= 10, 7 can be divided into 2 and 5, 10+5= 15).
Note: the method that children like and are familiar with is the method, and only one can be mastered.
(2)20:
1 1+6 (increased digits,1+6 = 7)11+6 =17.
15-3 (the quantity is reduced enough, 5-3=2) 15-3= 12.
3. Strengthen the training of lifting, not lifting and not giving way.
4. When looking at the picture to solve the problem, we should use the known conditions in the picture to formulate correctly. Commonly used relationships are:
(1) number of copies+number of copies = total: at this time? Under the bracket in the middle.
(2) Total number-number of parts = number of other parts: at this time? On the upper side of the bracket.
(3) Large number-decimal number = difference: who is more than who, or who is less than who.
(4) Original-Lending = Remaining: Use as much as you need.