1, mental arithmetic: Through training and practice, you can improve your mental arithmetic ability. This includes basic operations such as addition, subtraction, multiplication and division through mathematical skills and calculation rules.

2. Approximation method: When complex calculation is needed, approximation method can be used to simplify the problem. For example, approximate a number to a number that is easier to calculate and then calculate it.

3. Decomposition method: A complex problem is decomposed into a series of simple calculation steps. By calculating and merging the results step by step, the final answer is finally obtained.

4. Simplify the problem: For complex calculation, the amount of calculation can be reduced by simplifying the problem. For example, using mathematical properties to simplify and reduce the steps of multiplication and division.

5. Apply laws: discover and apply mathematical laws and patterns to simplify calculations. For example, by using the commutative law and associative law of multiplication, the calculation order is adjusted to a more manageable form.

Off-line computing algorithm

1, multiply first and then divide, then add and subtract.

2. In the 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.

3. In the demoulding process, the operation sequence line should be drawn according to the operation sequence, and the "three inspections" should be achieved.

First, 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.