1, the divisor is unchanged, three digits are regarded as hundreds, tens or even hundreds, and then calculated by the basic method of oral calculation.

2. Splitting number estimation method.

Divide three digits by hundreds plus dozens or hundreds plus dozens (the number divided is usually a multiple of one digit), and then add the divided quotients.

3. I want to estimate.

Think of a number multiplied by a number that is closest to or equal to the highest or first two digits of the dividend. One hundred or dozens is the quotient to be estimated.