I. Unit 1

1, 10 ten thousand is one hundred thousand, 10 ten thousand is one million, 10 one million is ten million, 10 ten million is one hundred million. The forward rate between two adjacent counting units is "ten", which is called decimal counting method. Special attention: the difference between counting units and numbers.

2. When using numbers to represent numbers, these counting units should be arranged in a certain order, and their positions are called numbers.

3. Number of digits: A number contains several digits, that is, several digits. For example, 652 100 is a six-digit number.

According to our country's counting habit, every four digits are counted from the right.

Second, the second unit

1, the pen calculation method of multiplying three digits by two digits: first multiply three digits by two digits, and the last digit of the product is aligned with the two digits; Then multiply the three digits by the number on the ten digits of the two digits, and the last digit of the product is aligned with the ten digits of the two digits; Finally, add the products of the two multiplications.

2. Law of product change: If one factor remains unchanged, another factor is multiplied (or divided) by several (except 0), and the product is also multiplied (or divided) by several.

3. The price of each commodity is called the unit price; How much did you buy? A * * * price is called the total price. Unit price × quantity = total price. Unit price = total price ÷ quantity.

Three. Unit 3

1. Two straight lines that do not intersect in the same plane are called parallel lines, or they are parallel to each other. Note: A∑b is pronounced as: A and B are parallel.

2. When two straight lines intersect at right angles, they are said to be perpendicular to each other, one of which is called the perpendicular of the other, and the intersection of these two straight lines is called the vertical foot. Note: a⊥b, pronounced as: A is perpendicular to B.

3. The shortest vertical line drawn from a point outside a straight line is called the distance from the point to the straight line.

4. The line segments perpendicular to two parallel lines are equal in length. Or: the distance between two parallel lines is equal everywhere. You can draw a straight line by taking a point (or an outer point) on the straight line as a vertical line.