1, and the rounding method in integer operation is the same. In the fractional operation, four algorithms (such as commutative law, associative law and distributive law) are fully used to make partial sum, difference, product and quotient become integers and integer ten ... thus simplifying the operation.

2. In an expression with only addition and subtraction operations, add brackets to a part of the expression. If there is a plus sign in front of the brackets, the operation symbols in the brackets will not change; If there is a minus sign in front of the parentheses, the operation sign in the parentheses will change, that is, the plus sign will change to the minus sign, and the minus sign will change to the plus sign.

3. In the addition and subtraction formula with brackets, delete the brackets in the formula. If there is a plus sign in front of the bracket, the operation symbol in the bracket will remain unchanged after the bracket is removed; If there is a minus sign in front of the parentheses, the operation sign in the parentheses will change, that is, the plus sign will change to the minus sign, and the minus sign will change to the plus sign.