1. Divide from the high order of the dividend, and try the first digit of the dividend with the divisor every time. If it is less than the divisor, try the division of the first two digits again.

2. In division with remainder: the minimum remainder is1; The remainder of is divisor minus1; The smallest divisor is the remainder plus 1.

3. Quotient× Divider = Divider Quotient× Divider+Remainder = Divider.

4. Estimation of division: In real life, sometimes you don't need to calculate the exact result, but treat some numbers as integers close to it, and then calculate them. This calculation is called estimation.

5. Angle, pentagram, isosceles triangle, equilateral triangle, isosceles trapezoid, square, rectangle, circle and regular polygon are all axisymmetric figures.

It is an abstract concept for counting, marking or measuring, and it is a simple symbolic record form (or measurement) of things with the same nature or homogeneity.

A series of symbols representing numbers, including numbers and operation symbols, are collectively called the numeration system. In daily life, numbers usually appear on signs (such as roads, telephone numbers and house numbers), serial indicators (serial numbers) and codes (ISBN). In mathematics, the definition of number is extended to include abstract concepts such as fraction, negative number, irrational number, transcendental number and complex number.