2. Flexible use of "the meaning of multiplication" can skillfully calculate some operations of multiplying multiple digits by two digits.

3. Using the "quotient invariance" property to calculate skillfully in the division operation, if the divisor is a special number such as 5, 25 or 125 or their multiples, we can use the "quotient invariance" property to calculate skillfully, which will get twice the result with half the effort. The "quotient invariant" property: the dividend and divisor are multiplied or divided by a number (except 0) at the same time, and the quotient is invariant.

4. Disassemble or combine "dividends" for clever calculation.

5. In the related operations of division, in addition to applying the property of "quotient invariance", the following laws can also be applied for ingenious calculation. Law: After dividing the dividend into the sum (or difference) of two numbers, you can divide the two numbers by the divisor, and then find the sum (or difference) of the two quotients, and the result remains unchanged.