The main thing to master in disjoint calculation is to remember to calculate multiplication and division first, and then add and subtract. In the successive calculation of multiplication and division, it should be calculated from left to right. When you encounter parentheses, you must first calculate the inside of parentheses.
In the process of separation, we should draw the operation sequence line according to the operation sequence, and do a good job of "three checks": first, we should check whether the numbers and symbols copied from books to exercise books are correct; The second is to check whether the numbers and symbols copied from horizontal to vertical are correct; Third, it is necessary to check whether the draft is copied vertically, horizontally, and whether the decimal point position is correct or not.
Mathematically speaking, the order of these four operations is as follows:
(1) peer operation:
In an equation, if it only contains the same level of operations, it should be operated 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) Primary to secondary operations:
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 as {}. 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, you should first calculate the formulas in brackets in the order mentioned above, and then calculate the results in the order of the numbers outside brackets.