The first unit negative number

1. In order to represent two opposite quantities, a new number appears here:-16. -500. Numbers like-16, -500, -3/8, -0.4 are called {negative numbers}. -3/8 is pronounced negative.

2. Numbers 16, 2000, 3/8, 6.3, ... are called {positive numbers}. Positive numbers can also be preceded by a+sign, such as+16, +3/8. +6.3 and so on. (You can also omit the+sign) +6.3 is pronounced +6.3.

3.0 neither positive nor negative.

4. All positive numbers are on the left of 0, that is, negative numbers are less than 0, positive numbers are greater than 0, and negative numbers are less than positive numbers.

Unit 2 Cylinders and Cones

1. The two circular surfaces of the cylinder are called the bottom surface; The surrounding surface is called the side surface; The distance between two bottom surfaces is called height.

2. The surface area of the cylinder = the side area of the cylinder+the areas of the two bottom surfaces.

3. lateral area of cylinder = perimeter of bottom circle x height vXs h.

4.v cone = 1/3v cylinder = 1/3sh.

Third unit ratio

1. I like it (the national flag on the playground is 2.4:1.6 = 3/2; The national flag in the classroom is 60:40=3/2, so 2.4: 1.6=60:40 can also be written as 2.4/ 1.6=60/40.

2 The four numbers that make up a proportion are called proportional items. The two terms at both ends are called external terms of proportion, and the two terms in the middle are called internal terms of proportion.

3. In proportion, the product of two external terms is equal to the product of two internal terms, which is called the basic property of proportion.

4. According to the basic nature of proportion, if you always take any third item in proportion, you can find another unknown item in this proportion. Finding the unknown term in the proportion is called the solution ratio.

Because the bottom area of the cup is fixed, the volume of water varies with the height. As the height of water increases, its volume also increases; As the height of water decreases, its volume also decreases. Moreover, the ratio between the volume and the height of water is certain, so we say that the volume and the height are {proportional}, and the volume and the height are called {proportional}.

6. If the letters X and Y are used to represent two related quantities and K is used to represent their ratio (certain), the positive proportional relationship can be expressed as y/x=k (certain).

7. Positive proportion in life: the quality and volume of water are directly proportional; If the width of a rectangle is constant, then the area of the rectangle is proportional to its growth.

8 .. Because the volume of water is constant, the height of water changes with the change of bottom area. The bottom area increases, the height decreases, the bottom area decreases and the height increases. Moreover, the product of height and bottom area is certain, so we say that height and bottom area are inversely proportional, and height and bottom area are called inverse proportional quantities.

9. If the letters X and Y are used to represent two related quantities and K is used to represent their product (certain), the inverse relationship can be x X y=k (certain).

10. The north distance between a picture and the actual distance is called the {scale} of this picture.

1 1. According to: distance on map/actual distance = scale, equations can be listed.

12. Because the price per ton of water is fixed, the water fee is directly proportional to the water consumption. In other words, the ratio of water fee to water consumption of the two companies is equal.

13. Because the total number of books is certain, the number of packages is inversely proportional to the number of books in each package, that is, the product of books and the number of packages in each package is equal.

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