When there are both multiplication and division and addition and subtraction, multiply first and then divide, and then add and subtract.
When there are brackets, count the inside of the brackets first, and then the outside of the brackets.
When there are multiple brackets, count the brackets first, then the brackets inside, then the braces inside, and finally the brackets outside.
In the process of separation, the operation sequence line should be drawn according to the operation sequence, and the "three checks" should be done well. First of all, check whether the numbers and symbols copied from books to exercise books are correct. Second, check whether the numbers and symbols copied from horizontal to vertical are copied correctly. Third, it is necessary to check whether the draft is copied vertically, horizontally, and whether the decimal point position is correct or not.
Four ways of operation
1, sibling operations In an expression, if only sibling operations are included, operations should be performed from left to right. That is to say, only addition and subtraction, or only multiplication and division are mixed operations, and their operation order is calculated from left to right.
2, the first to second level operation
In an expression, if both first-level operation and second-level operation are included, then the second-level operation should be calculated first, and then the first-level operation should be calculated. That is, "multiply first and then divide, then add and subtract", or "multiply first and then divide, then add and subtract" for short.
3. Operation with brackets
If you want to change the order of the operations mentioned above, you need to use parentheses. There are three kinds of brackets commonly used: parentheses, marked as (); Parentheses, marked []; Braces, marked {}. When using the bracket, pull on both sides and add in the middle. Use parentheses first, then brackets, and finally braces.
If there are several kinds of parentheses in an expression, the multiplication or division in parentheses should be calculated first, then the addition or subtraction in parentheses, and finally the parentheses. When calculating, the formulas in brackets should be calculated in the order mentioned above, and then the results should be calculated in the order of numbers outside brackets.