(1) area and area unit:
1, find out the connection and difference between length unit and area unit;
2. Carefully examine the questions, and explicitly ask for it again.
(2) Calculation of rectangular and square areas:
1, squared: (a) perimeter = side length ×4- Use length units.
(b) Area = side length × side length-use area unit
2. Rectangle: (a) Perimeter = (length+width) ×2- Use the unit of length.
(b) Area = length× width-use area units.
(3) the forward speed between regional units
1, length unit: meter, decimeter and centimeter-the speed is10; 1 m = 10 decimeter =100 cm =1000 mm.
2. Area unit: square centimeter, square decimeter and square meter-the propulsion rate is100;
1 m2 = 100 cm2, 1 cm2 = 1 0000 cm2,1m2 = 10000 cm2;
3. "hectares" (measuring the area of vegetable fields and orchards) and "square kilometers" (measuring the area of urban land) are larger units for measuring land;
4. Mass units: grams (g), kilograms (kg, also called kilograms) and tons (t). 1000g = 1 kg,1000kg = 1 ton.
5. When measuring distance or measuring relatively long objects such as railways and rivers, it is generally in kilometers, also called kilometers. (4) The characteristics of each figure: the characteristics of a rectangle: the opposite sides are equal, and the four corners are right angles;
The characteristics of a square: four sides are equal and four corners are right angles;
Characteristics of parallelogram: two groups of opposite sides are parallel and equal.