1, the first unit length unit: common length units: meters and centimeters. The unit of measurement for shorter objects is usually centimeters, and the unit of measurement for longer objects is usually meters. Method of measuring the length of an object: aim the left end of the object at the "0" scale of the ruler and see what the scale of the right end of the object is on the ruler. The length of this object is several centimeters. The relationship between meter and centimeter: 1 meter = 100 cm 100 cm = 1 meter. Fill in the appropriate length unit for the line segment.

2. Addition and subtraction in unit 100: two digits plus two digits; Two digits minus two digits; Addition, subtraction, addition and subtraction; Solve problems (application problems).

3. Unit 3 Preliminary Understanding of Angle: Preliminary Understanding of Angle; A preliminary understanding of right angles.

4. Unit 4 and Unit 6 table multiplication (1) and (2): the meaning of multiplication.