First unit length unit
Summary of knowledge points:
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: align the left end of the object with the "0" scale of the ruler to see what the scale of the right end of the object is on the ruler. The length of this 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.
⑵ Method of drawing line segments: first aim the pen at the' 0' scale of the ruler, 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.
(3) When measuring the length of an object, when the measurement is not started from the "0" scale, the scale number of the starting point should be subtracted from the scale number of the end point.
6. Fill in the appropriate length unit.
Xiaoming is 1 (m) 30 (cm) tall, his exercise book is 13 (cm) wide, and his pencil is 17 (cm).
Blackboard length 2 (m) Thumbnail length 1 (cm) A bed length 2 (m).
Jingshen 3 (meter) School Run 100 (meter) Competition. The teaching building is 25 meters high.
The baby is 80 (cm) tall, the skipping rope is 2 (m) long, and a tree is 3 (m) tall.
A key is 5 cm long, a pencil box is 24 cm long and the platform is 90 cm high.
The door is 2m high, the classroom is12m long, and the chopsticks are 20cm long.
Unit 2 100 internal number addition and subtraction
Summary of knowledge points:
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.
3. When writing, add two numbers, and the same numbers should be aligned. Starting from single digits, add "1" to the tenth digit for every full digit. Don't leave out "1" when adding the tenth digit.
4. Sum = Appendix+One Appendix = and-Another Appendix
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 = minuend-Meimei = Meimei+Differential Meimei = Meimei+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. Add and subtract estimates
In daily life, we don't need accurate calculation, we just need to work out a rough result. In this case, we need to estimate. When estimating, estimate this number to the nearest integer ten and then calculate.
4. 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. The application problem of seeking more than the number is added; Find an application problem with a number less than one and calculate it by subtraction (note: subtract a large number).
3. On the topic of questioning, you can ask questions like this:
(1) ... and ... a * * * ...?
(2) ... How much more than ...?
(3) ... How much less than ...?
A preliminary understanding of the third unit angle
Summary of knowledge points:
1, angle: red scarf, triangle, clock face, other objects have different angles.
2. Names of parts of an angle: An angle has a vertex and two sides. As shown on the right. pinnacle
3. Characteristics of the angle: ① One vertex and two sides (both sides are straight); ② Its two sides are rays, not line segments; (3) The ray has only one endpoint, so the length cannot be measured.
4. Method of drawing an angle with a ruler: When drawing an angle, first determine a point, and draw two lines in different directions with a ruler to draw an angle.
5. The angle has nothing to do with the length of both sides, but only with the width of both sides.
6. The bigger the sides of the angle, the bigger the angle.
The order from small to large is 123.
7. Method of drawing a right angle: ① Draw a point ② Draw a straight line from this point.
(3) A right-angled edge of the triangular plate coincides with the drawn straight line, and the right-angled vertex coincides with the drawn point.
④ Draw a straight line along the other right angle of the triangle ⑤ Mark the right angle symbol after drawing the right angle.
8. To know whether an angle is a right angle, you can compare it with the right angle on a triangle: vertex to vertex, one side to one side, and then look at the other side.
9. Of the three angles on a triangle, 1 is a right angle. Both a square and a rectangle have four corners, which are right angles.
Unit 4 Table Multiplication (I) and Unit 6 Table Multiplication (II)
Summary of knowledge points:
1, the meaning of multiplication
Multiplication is a simple algorithm to calculate the sum of several identical addends. For example: calculation: 2+2+2=6, calculation by multiplication: 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.
︰ : : : : :
The number with the same addend and the number with the same addend are the sum of the same addend.
⑵ Read multiplication formula. When reading multiplication formulas, read them in the formula order. For example, 6×3= 18 is read as "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 multiplication and the number after multiplication are called "factors"; The number after the equal sign is called the 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. For example:
4×5 means five 4+ or four 5+.
When addition is written as multiplication, the sum of addition is equal to the product of multiplication.
6. In the multiplication formula, two factors exchange positions and the product remains unchanged.
7. Names and calculation formulas of each part of the formula.
Multiplication: factor × factor = product
Addition: appendix+appendix = sum-appendix = appendix.
Subtraction: subtraction = difference subtraction = difference+subtraction-subtraction = subtraction-difference.
8. In the multiplication formula of 9, 9 multiplied by 9 or 9 multiplied by several can be regarded as tens minus several, where "several" refers to the same number.
Such as:1× 9 =10-1.9× 5 = 50-5.
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:
Plus: 3+3+3+2 = 14 times: 3×4+2= 14 times minus: 3×5- 1= 14.
10, "How many times is a number" is calculated by multiplication, using: this number × multiple or multiple × this number.
1 1, there are several identical addends, which are several times the same addend. For example, three fives is three times as much as five. Unit 5 Observing Objects
I. Axisymmetric figure and axis of symmetry
1. If a graph is folded in half along a straight line, the graphs on both sides can completely overlap. This figure is an axisymmetric figure, and the straight line where the crease is located is called the axis of symmetry.
2. The parts on both sides of the symmetry axis can completely overlap if they are the same in shape, size, position and direction.
3. Draw the symmetry axis with a dotted line.
4. Rectangular, square and circle are symmetrical figures.
A rectangle has two axes of symmetry. A square has four axes of symmetry. A circle has countless axes of symmetry.
Second, mirror symmetry.
For example, the reflection of the lake and looking in the mirror are mirror images. The reflection of the lake is symmetrical with respect to the horizontal plane, while looking in the mirror is symmetrical with respect to the vertical plane. When looking in the mirror, the up and down, front and back positions of people inside and outside the mirror will not change, but the left and right positions will be reversed.
Third, add symmetrical graphics.
When drawing the other half of a symmetrical figure, you can first find the symmetrical points of the two ends of each line segment in the grid, and then connect them with straight lines. The symmetry point of a point on the axis of symmetry is still this point. The symmetry axis is vertical, and the figure is symmetrical left and right; The symmetry axis is horizontal, and the figure is symmetrical up and down.