Knowledge points of second grade mathematics
1, length unit: refers to the basic unit for measuring spatial distance, which is formulated by human beings to standardize the length. Its international unit is "meter" (symbol "m"), and commonly used units are millimeter (mm), centimeter (cm), decimeter (dm), kilometer (km) and so on. Length units play an important role in various fields.
2. meter: in the international system of units, the standard unit of length is "meter", which is represented by the symbol "m".
3. decimeter: dm is one of the metric units of length, and 1 decimeter is equivalent to one tenth of 1 meter.
4. centimeter: centimeter, length unit. The abbreviation (symbol) is cm.
Unit conversion of centimeters:1cm =10 mm = 0.1decimeter =0.0 1 m =0.0000 1 km.
5, MM: English abbreviation mm (or mm, ㎜)
Clearance at the entrance:1mm = 0.1cm;
6. Carry: In addition, when each digit is equal to the radix, move forward by one digit.
For example, if the number of digits reaches 10, the number will move forward by 1 to become a ten.
In the decimal algorithm, if every digit is full ten, add1to the decimal digit; When there are ten people to ten, add one to a hundred.
7. subtraction without abdication: subtraction without high position. For example: 56-22=34. You can subtract 2 from 6, so you don't have to borrow the first 5.
8. abdication subtraction: the subtraction operation that must borrow from the high position. For example: 5 1-22=39.
1 cannot be reduced by 2, but must be borrowed from Gao 5.
9. Continuous addition: The continuous addition of multiple numbers is called continuous addition. For example: 28+24+23=85.
10, continuous subtraction: the continuous subtraction of multiple numbers is called continuous subtraction. For example: 85-40-26= 19.
Knowledge points of mathematics in the second grade of primary school
First, understanding the angle.
1, characteristics of an angle: one vertex and two sides (straight)
2. The size of the angle is related to the size of both sides, and has nothing to do with the length of both sides.
3. The angle of painting:
(1) Fixed Vertex.
(2) Draw a straight line from this point.
(3) Draw another side (at right angles, aim at the drawn side with the right angle side and draw a line along the other right angle side).
Second, the classification of angles:
1, understanding right angles: the characteristics of right angles,
2. Know acute angle and obtuse angle: acute angle is less than right angle, and obtuse angle is greater than right angle.
3. You can judge the right angle, acute angle and obtuse angle with a triangular ruler: overlap the vertex of the right angle on the triangular ruler with the vertex of the compared angle, then overlap one side of the right angle on the triangular ruler with one side of the compared angle, and finally compare the other side of the right angle on the triangular ruler with the other side of the compared angle. This line is a right angle, the inside is an acute angle and the outside is an obtuse angle.
4. Draw right angles, acute angles and obtuse angles.
Knowledge points of quadrilateral understanding in mathematics of grade two in primary school
Rectangular and square
Knowledge points:
1, master the characteristics of rectangular squares: both rectangles and squares have four sides, four right angles, the opposite sides of the rectangle are equal, and the four sides of the square are equal.
2. Understand the relationship between rectangle and square: square is a special rectangle.
3. Can draw rectangles and squares on grid paper.
parallelogram
Knowledge points:
1, intuitively understand the parallelogram, and know that the parallelogram has four sides, four corners, and the opposite sides are equal.
2. Understand that a rectangle is a special parallelogram.
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