1. A ruler is a tool for measuring the length of an object. Commonly used length units are: meters and centimeters. The index finger is about 1 cm wide and the arms are about 1 m. 1m = 100cm 100cm = 1m。

2. The measurement unit of shorter objects is usually centimeters, and the measurement unit of longer objects is usually meters.

3. When measuring the length of the object: aim the "0" scale of the ruler at the left end of the object, and then see how many centimeters the right end faces the scale. Object length = large number-decimal number, for example, from scale "0" to scale "6" is 6 cm (6-0=6), and from scale "6" to scale "9" is 3 cm (9-6 = 3); You can also calculate the length of an object by counting. (Count, count)

4. The line segment is straight and its length can be measured.

5. Method of drawing line segments: Draw from the "0" scale of the ruler, the longer the better. (find some lines; Sometimes you have to work out the length before drawing a line. Draw a line 2 cm shorter than 6 cm. )

6. This angle has 1 vertices and two straight sides. Acute angle is less than right angle, obtuse angle is greater than right angle, and obtuse angle is greater than acute angle. Acute angle).

7. You can draw a right angle with a triangle, and the right angle should be marked with a right angle symbol (also called the vertical foot symbol).

8. All right angles are the same size. To know whether an angle is a right angle, you can compare it with the right angle on a triangle. A rectangle and a square have four corners, all of which are right angles.

9. The angle has nothing to do with the length of both sides, but with the size of both sides.

10, each triangle has three angles, of which 1 is a right angle and the other two are acute angles.

1 1, Angle drawing: Starting from one point, draw two straight lines in different directions with a ruler to draw an angle. A figure composed of two rays drawn from a point is called an angle. )

Second, the written addition and subtraction knowledge points within 100:

1. When calculating the vertical addition of two numbers: align the same numbers. Start with the unit. If the number of digits exceeds 10, enter 1 at the tenth digit.

2. When calculating the two-digit subtraction vertically: align the same numbers. From a place. If the number of digits is not enough, subtract 1 from the ten digits to form two digits, and then subtract. Remember to subtract 1 when calculating ten digits.

3, add and subtract mixed operation, according to the order from left to right, there are parentheses, calculate the parentheses first, and calculate by steps.

4. How much is "one known number" more than "another known number"? Calculate by subtraction, such as how much is 70 more than 25? How much is 19 less than 46

5. How many questions are there? If there are more unknowns than anyone else, add a few more. /kloc-how much is 0/7 more than 29? (29+ 17=46)

Third, the multiplication knowledge points in the table [be sure to memorize the multiplication formula and use it skillfully. ]

1, it is easier to find the sum of several identical addends and express it by multiplication. The simple operation of finding the sum of several identical addends is called multiplication.

2. rewriting of addition and multiplication, such as: 5+5+5+5 written as multiplication formula: 5×4 or 4× 5; Conversely, multiplication can also be rewritten as addition. For example, 8× 4 = 8+8+8 (if you forget the multiplication formula or remember it wrong, you can rewrite the multiplication formula into an addition formula to calculate it. When addition is written as multiplication, the sum of addition is equal to the product of multiplication.

3.2×7= 14 pronounced as: 2 times 7 equals14; 3 times 4 equals 12. Writing: 3×4= 12.

4. In the multiplication formula, two multipliers (factors) exchange positions, and the product remains unchanged. For example: 8×4=4×8

5. Look at the picture and write the multiplication, addition and subtraction formulas:

Multiplication and addition: the same part is represented by multiplication first, and then the different parts are added. Calculate the same first and then add the difference. Multiplication and division: first calculate each copy as the same number, write it as multiplication, and then subtract the extra number. For example: addition: 5+5+5+5+3=23 times plus: 5×4+3=23 times minus: 5×5-3=23.

6. "What is the sum of several additions" and "What is the multiple of a number" are all calculated by multiplication, for example, what is the triple of 7? (7×3=2 1), what is the sum of five eights? (8×5=40)

Fourth, the knowledge points of the observation object [front, side, top. ]

1. When you look at a three-dimensional figure from the front, you see a rectangle. This three-dimensional figure may be a cuboid or a cylinder.

2. One side of the three-dimensional figure you see is a square. This three-dimensional figure may be a cube or a cuboid.

3. A face in the perspective you see is round. This three-dimensional figure can be a sphere, a cylinder or a cone.

The objects seen face to face have the same shape, but the directions are opposite.

5. When observing the surface of the combined object, it has nothing to do with the height and arrangement of the object.

Five, know the time knowledge points

1, 1 =(60) points.

2. The number upstream of the clock face (12), which divides the clock face into (12) equal grids, and each grid is divided into (5) equal grids, and there are (60) small grids on the clock face.

There are (2) hands on the clock face. The shorter needle is called (hour) needle, and the longer needle is called (minute) needle. When the minute hand walks at 1, it is (1) minutes, when the big hand walks at 1, it is (5 minutes), and when the hour hand walks at 1, it is (1). Minute hand from 12 to 6, go (30 points); The clockwise clock went from 12 to 6, and walked for (6) hours; Clockwise hand made a circle from 12, then returned to 12 and left (12).

4. (30) minutes can also be said to be half an hour, and (15) minutes can also be said to be a quarter of an hour. For example, 8: 30 is 8: 30, and 9: 00 15 is 9: 15.

At 5 o'clock (3 o'clock or 9 o'clock), the hour hand and the minute hand on the clock face are at right angles.

6. Write down the time on the clock face and draw the minute hand: the third question of the textbook is P 10 1, and the sixth question is P 105.

Six, mathematics wide-angle knowledge points

1, when arranging combinations, according to a certain order, so as to avoid duplication or omission. Arrangement is related to order, such as the composition of numbers, the collocation of clothes and trousers, breakfast, queuing and so on. Combination has nothing to do with order, such as digital summation, handshake, juice mixing and so on.

2, 3 people, every two people play a game or shake hands and take pictures. * * * to 3 times.

3. Three nonzero numbers can form six tens and two digits with different digits, such as 4, 5 and 7 can form 45, 47, 54, 57, 74 and 75; If one is 0, it can form four two-digit numbers. For example, 0, 4 and 7 can form 40, 47, 70 and 74.