1, commonly used length units: meters and centimeters.

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

3. Method of measuring the length of an object: aim the left end of the object at the ruler? 0? Scale, look at the scale of the right end of the object facing the ruler. The length of the object is several centimeters.

4. Relationship between meter and centimeter: 1 meter = 100 cm 100 cm = 1 meter.

5. Line segment

⑴ Characteristics of the line segment: ① The line segment is straight; ② The line segment has two endpoints; ③ The length of the line segment can be measured.

(2) the method of drawing line segments: first aim the pen at the ruler? 0? Scale, point a point on the top, then aim at the centimeter scale of the length to be drawn, point a point on the top, and then connect the two points to write the length of the line segment.

(3) When to measure the length of an object? 0? When measuring the scale, subtract the scale of the starting point from the scale of the end point.

6. Fill in the appropriate length unit.

Xiaoming's height 1 (m) 30 (cm).

The width of the exercise book is13cm.

Pencil length 17 (cm)

Blackboard length 2 (m) Thumbnail length 1 (cm)

The bed is 2 meters long and the well is 3 meters deep.

The school has a 100 (meter) race.

The teaching building is 25 meters high and the baby is 80 centimeters high.

Jumping rope is 2 meters long and a tree is 3 meters high.

A key is 5 cm long.

A pencil box is 24 cm long.

The platform is 90 cm high.

Door height 2m, classroom length12m.

Chopsticks are 20 centimeters long.

A tree seedling is 1 (m) high.

The children's head circumference is 48 cm.

Dad's height 1.75 cm or 175 cm.

The height of children is 120cm or1.20cm..

Unit 2 Addition and subtraction within 100

One, two digits plus two digits

1, two-digit plus two-digit non-carry addition calculation rule: align the same numbers vertically, and then add the numbers on the same numbers.

2. The calculation rules of two-digit plus two-digit carry addition: ① the same digits are aligned; (2) from the unit; (3) exactly ten into ten equals 1.

When writing the addition of two numbers, the same number should be aligned, starting from the single digit and moving to the tenth digit every time it exceeds ten digits? 1? Don't leave out what happens when the tenth digit is added. 1? .

4. Total = Appendix+Appendix

One addend = and-the other addend.

Two digits minus two digits.

1, two-digit subtraction without abdication: the same number is vertically aligned, and then the number on the same number is subtracted.

2. Written calculation rules for two-digit subtraction and two-digit abdication subtraction: ① Same digit alignment; (2) from the unit; (3) If the number of digits is not enough, extract 1 from the ten digits, add 10 to the number of digits and subtract it.

3. When writing, subtract two numbers from two numbers, and align the same numbers. Starting with single digits, single digits are not enough. Starting from the tenth digit, subtract 1, add 10 to the single digit and then subtract. When calculating ten digits, the backward 1 should be subtracted before calculation.

4. Difference = minus-minus

Negative = negative+difference

Subtraction = minuend+difference

Third, add and subtract and add and subtract.

1, plus or minus

The writing order of addition and subtraction is the same as that of oral calculation, which is calculated from left to right in turn.

(1) The addition calculation can be done step by step or vertically. The calculation method is the same as adding two numbers. All the same numbers should be aligned, starting with single digits.

② The continuous subtraction operation can be calculated step by step or written as vertical calculation. The calculation method is the same as subtracting two numbers. The same numbers should be aligned, starting with single digits.

2. Add, subtract and mix

The operation order of mixed addition and subtraction formula is the same as vertical writing and addition and subtraction.

3. When writing vertically, you can calculate the mixed operation of addition and subtraction step by step. The method is the same as adding (subtracting) two numbers. The same number of digits should be aligned and counted from single digits. You can also write in a simple way, in a vertical row. First, complete the calculation of the first step, and then add (subtract) the second number with the result of the first step.

Fourth, solve the problem (application problem)

1, steps: ① Look at the horizontal questions first, write the results, and don't forget to write the unit (the unit is: how much or the words behind) ③ Answer.

2. ask? A known number? Than? Another known number? More or less? Calculate by subtraction. Use? Than? Subtract the smaller numbers from the larger numbers on both sides of the word.

3, a number of more than a few, less than a few, to find this number. First, analyze the key sentences. Than? Is the word preceded by a large number or a decimal number? Than? Whether the word is followed by a large number or a decimal, the question requires a large number or a decimal. Add up large numbers and subtract decimals.

4. On the topic of questioning, you can ask questions like this:

(1). There is another * * *?

② How much/how much more ...?

How much less than ...?

A preliminary understanding of the third unit angle

A preliminary understanding of 1 and angle

(1) Angle consists of a vertex and two sides;

(2) Angle drawing method: Starting from one point, draw two straight lines in different directions with a ruler.

(3) The size of the angle is not related to the length of the side, but related to the size of both sides of the angle. The bigger the angle is, the bigger the angle is, and the smaller the angle is.

2. A preliminary understanding of right angles

(1) Judgment method of right angles: Compare right angles on a triangular ruler (vertex to vertex, one side to one side, and then see if the other side is coincident).

(2) Method of drawing a right angle: ① Draw a vertex first, then draw a straight line from this point ② Align this point with the vertex of the right angle on the triangular ruler, and align a right angle edge with this line ③ Draw a line ④ from this point along another right angle edge on the triangular ruler, and finally mark the right angle mark.

(3) Acute angle is less than right angle, obtuse angle is greater than right angle: acute angle.

(4) All right angles are equal.

(5) Each triangular ruler has 1 right angle and two acute angles. There are three angles on the red scarf, one is obtuse and the other is acute. Rectangular and square have four right angles.

Unit 4 and Unit 6 table multiplication (1) and (2)

1, the meaning of multiplication

Multiplication is a simple algorithm to calculate the sum of several identical addends. For example, the calculation: 2+2+2=6, and the multiplication is: 2? 3=6 or 3? 2=6.

2. Writing and reading multiplication formula.

(1) A method of rewriting a continuous addition formula into a multiplication formula. Find the sum of several identical addends, which can be calculated by multiplication. When writing multiplication formula, you can use multiplication operation. When writing a multiplication formula, you can write the same addend first, then the multiplication symbol, then the number of the same addend, and finally the equal sign and the addition. You can also write the number of the same addend first, then write the multiplication symbol, then write the same addend, and finally write the sum of equal sign and continuous addition.

For example, 4+4+4= 12 is rewritten as a multiplication formula of 4? 3= 12 or 3? 4= 12

4 ? 3 = 12 or 3? 4 = 12

⑵ Read multiplication formula. When reading multiplication formulas, read them in the formula order. Such as: 6? 3= 18 pronunciation:? 6 times 3 equals 18? .

3. The names and practical significance of each part in the multiplication formula.

In the multiplication formula, the number before the multiplication sign and the number after the multiplication sign are both called? Multiplier? ; What's the number after the equal sign? Product? .

4, the meaning of multiplication formula

It is relatively simple to find the sum of several identical addends by multiplication. The multiplication formula represents the sum of several identical addends. Such as: 4? 5 means five fours or four fives.

When addition is written as multiplication, the sum of addition is equal to the product of multiplication.

6. In the multiplication formula, two multipliers exchange positions and the product remains unchanged.

7. Names and calculation formulas of each part of the formula.

Multiplication: Multiplier? Multiplier = product

Addition: Appendix+Appendix = Sum.

And then what? Appendix = Addendum

Subtraction: minuend? Subtraction = difference

Subtraction = difference+subtraction

Subtraction = minuend? poor

8. In the multiplication formula of 9, multiplying by 9 or multiplying by 9 can be regarded as tens of MINUS several, in which? How many? Refers to the same number.

Such as: 1? 9= 10? 1 9? 5=50? five

9. 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.

Multiplication and division: first calculate each copy as the same, write multiplication, and then subtract the extra part.

When calculating, multiply first, then add, and then subtract.

For example: addition: 3+3+3+2 = 14 times plus: 3? 4+2= 14 plus or minus: 3? 5- 1= 14

10、? How much and how much add up? With what? How much does it add up to? different

Find a few plus a few, use a few plus a few; What is the sum of 4 and 3? By addition (4+3=7)

Find several sums and multiply them by several times.

What is the sum of four threes? (3+3+3+3= 12 or 3? 4= 12 or 4? 3= 12)

Supplement: How to calculate multiplication and quadrature? how much is it? How many/much? Like 2 plus 4 times 2? 4=8

What are the two multipliers, quadrature? how much is it? How many, like two eights multiplied by eight? 8=64

1 1, a multiplication formula can mean two things, such as? 4? 2? Can you express it? Four twos add up? Can you also express? Two fours add up? .

? 5+5+5? Written multiplication formula is (3? 5= 15) or (5 3= 15),

It can be calculated by formula (35 15), that is, items (3) and (5) are added.

3? 5= 15 Pronunciation: 3 times 5 equals 15. 5? 3= 15 Pronunciation: 5 times 3 equals 15.

Unit 5 Observing Objects

1, observing the same object from different angles, the shape of the object you see is generally different;

2. When observing an object, we should grasp the characteristics of the object to judge.

Look at one side of a cuboid, and you may see a rectangle or a square. When you look at one side of a square, all you see is a square.

4. Observe this cylinder, and you will see a rectangle or a circle. When you look at a sphere, all you see is a circle.

Unit 7 Knowing Time

1, know the time

(1) There are an hour hand and a minute hand on the clock face, which walk fast and the minute hand is long; Walk slowly, the shorter the hour hand;

(2) There are 12 large squares, 60 small squares and 1 large square with 5 small squares on the clock face. Walk clockwise 1 hour and walk in minutes.

(3) It takes one lap to walk clockwise 1, so 1 =60 minutes;

(4) Half an hour =30 minutes, and a quarter of an hour = 15 minutes.

(5) Time reading and writing: for example, 3: 30, which can be read as 3: 30 or 3: 30; 8: 05, you should write 8:05.

2. Solve problems with knowledge

(1) events should be arranged in chronological order, and the time cannot be repeated.

(2) When asked what time it is in a few minutes, read out what time it is now, and then calculate what time it is in a few minutes.

(3) The hours when the hour hand and the minute hand can form a right angle are 3 o'clock and 9 o'clock.

Unit 8 Mathematics Wide Angle-Collocation

1. When two different numbers (except 0) are combined, the positions of the two numbers can be interchanged; When three different arrays synthesize two digits, each digit (except 0) can be made into ten digits, and the other two digits can be combined with it in turn.

2. Answering questions with lines or symbols is relatively simple.

3. Arrangement is related to order, and combination has nothing to do with order.