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Try to divide the divisor by the integer ten or close to its integer hundred by rounding.

There are several ways to try business:

(1) rounding method. Try to divide the divisor by an integer ten or an integer hundred close to it. For example, if the divisor is 78, you can try to divide it as 80. Divider 723 can be regarded as 700 to try to divide.

(2) The "rounding" method means that when the divisor is rounded, the dividend will be rounded with the divisor, 54 can be regarded as 50, 432 as 400, and quotient 8 is correct. This is the exchange of dividend and divisor. Another example: the divisor is 58, the dividend is 290, and the quotient 58 can be regarded as 60.

(3) Numbers whose divisors are close to 15, such as 14, 15 and 16, and numbers whose divisors are close to 25, such as 24, 25 and 26, can be directly divided by 15 and 25, which can be reduced.

(4) Semi-estimated commercial law.

(5) The same head does not divide quotient nine, eight and seven.