Unit 1: Four sums 1. Calculate from left to right. Unit 2: Multi-digit reading: 1. 10 one is ten, 10 ten is one hundred, 10 ten thousand is one hundred thousand, 10 ten thousand is one million, and 10 one million is ten million, 655. 2. One, ten, one hundred, one thousand, ten thousand, one hundred thousand, one million, ten million, one billion, one billion ... these are all units of counting. Read level 10,000 before reading the next level. 4. Ten thousand series should be read as single series, followed by the word "ten thousand". 5. Each level has all zeros, and these zeros are not read. No matter how many zeros there are at the end of each level, don't read them. 7. All other numbers have a zero, or consecutive zeros are read-only 1 "zero". Write the number: 1. Write numbers from high places, first write billions, then tens of thousands, and finally tens of thousands. 2. Write 0 on any number without previous counting unit. Proportion size: 1. Compared with the highest bit, the number with the largest number in the highest bit is larger. If the highest bit is the same, it is higher than the next bit. We can use "ten thousand" or "hundred million" as the unit: 1. We can find the approximate figure by rounding. Unit 3: Add and subtract multiple digits with a calculator: 1. An electronic computer generally consists of a power supply, a switch, a display screen, a keyboard and an internal circuit. The relationship between addition and subtraction: 1. The sum of two numbers is calculated by addition, and the difference between two numbers is calculated by subtraction, which is the inverse operation of addition. Formula: one addend = and-the other addend is minuend = difference+divisor = minuend-difference addition algorithm: formula: additive commutative law: a+b=b+a addition association law: (a+b)+c=a+(b+c) addition distribution law: a-b-c = a- 2. Many lines can be drawn between two points, of which the line segment is the shortest and the length of the line segment is the distance between two points. 3. A line segment is a straight line with infinite extension at both ends, and the straight line has no vertex. 4. The infinite extension of a line segment is a ray, and the ray has only one vertex. 5. The figure composed of two rays drawn from a point is called an angle, the vertex is the vertex of the angle, and the two rays are the sides of the angle. 6. The angle is usually expressed by the symbol ∞, and its size can be measured by a protractor. Divide the semicircle into 180 parts, and the angle of each part is one degree, which is recorded as 1 "degree". 7. The center of the protractor coincides with the vertex of the angle, the zero scale line coincides with one side of the angle, and the scale of the other side of the angle on the protractor is 60 degrees, which is 60 degrees. 8. The two sides of an angle are just on a straight line, and such an angle is a right angle. 9. An angle less than 90 degrees is called an acute angle, and an angle greater than 90 degrees and less than 180 degrees is called an obtuse angle. A ray rotates 360 degrees around its vertex, which is called a fillet. Unit 5: Three digits times two digits. 1. When factor A amplifies factor A and factor A amplifies factor B, the product is amplified by a*b times. Written multiplication: formula: working efficiency * working time = total working speed * time = distance unit 6: intersection and parallelism 1. When two straight lines intersect at right angles, they are perpendicular to each other, and one of them is called the vertical foot of the other vertical line. 2. In the same plane, two lines that do not intersect are called parallel lines, and the two lines that make up parallel lines are parallel to each other. Unit 7: Three-digit division by two-digit division: Formula: Distance divided by speed equals time. Division: 1. Divide the first two digits of the dividend by the divisor first. If the first two digits of the dividend are less than the divisor, divide by the third digit. Besides the dividend, the quotient is written on the dividend. The remainder after each division operation should be less than the divisor. Exploration method: 1. The divisor remains the same, and the quotient of the dividend expands several times. 2. In the division formula, the divisor and divisor expand or shrink by the same multiple at the same time, and the quotient remains unchanged. This is the invariance of quotient.