The mixed operation of addition and subtraction is based on a single addition and subtraction operation. To learn the mixed operation of addition and subtraction well, you need to master two foundations:
First, the basic addition and subtraction operations should be skilled, which is the basis of the whole mathematical operation. The basic operation of addition and subtraction is the advance and retreat operation within 20. It is necessary to improve the oral calculation ability of addition and subtraction within 20, so that you can get the answer after reading the questions.
Second, you should be familiar with the operation order of addition and subtraction mixed operation. If there are no brackets, it should be calculated from left to right. If there are brackets, count the inside of the brackets first, then the outside. Many students did not calculate according to the operation method and order for the convenience of drawing, which led to calculation errors.
Elementary arithmetic law:
1, there is only addition and subtraction in the formula, then calculate it in turn; Only multiplication and division are calculated in turn.
2. There are both addition and subtraction operations and multiplication operations in the formula. Multiplication first, then addition and subtraction.
There are both addition and subtraction and division in the formula. Calculate division first, then add and subtract.
4, each step is not involved in the calculation of the part, to copy down the position and symbol unchanged, to ensure that the equal sign should be equal before and after.
5. The function of parentheses in mixed operation is to change the operation order. Operation sequence of mixed operation with brackets: first calculate the inside of brackets, then calculate the outside of brackets.
Operation sequence song:
The operation at the same level is the best, and it is calculated from left to right in turn. Two levels of operations appear, first multiply and divide and then add and subtract.
What should I do if I encounter parentheses? Parentheses count first, I will check every step, which will make me happy.