[Edit this paragraph] Mathematics

Proportion is a general term in technical drawing, which refers to the ratio between the linear size of a figure and its corresponding physical elements.

① Two formulas with equal ratios are called ratios, such as 3: 4 = 9: 12.

In 3: 4 = 9: 12, 3 and 12 are called external proportional terms, and 4 and 9 are called internal proportional terms.

There are four items in the proportion, namely two internal items and two external items.

2 ratio? For example, both teachers and students have met the requirements.

(3) Proportion, for example, among the goods sold, domestic products account for a relatively large proportion.

(4) After the proportion is written as a fraction, then the denominator on the left and the numerator on the right are internal terms.

The numerator on the left and the denominator on the right are external terms.

⑤ In a proportion, the product of two external terms is equal to the product of two internal terms, which is called the basic property of proportion.

⑥ Similarities and differences between proportion and inverse proportion.

The relationship between the same point and different points

In direct proportion, two related quantities, one of which changes and the other changes with it. If the ratio of two corresponding numbers in two quantities is certain, then these two quantities are called direct ratio, and the relationship between them is called direct ratio. If two related quantities are represented by the letters X and Y, and their proportional relationship is represented by K, it can be represented by the following sub: y/x=k (definite).

Inverse ratio of two related quantities, one quantity changes and the other quantity changes accordingly. If the product of two corresponding numbers is constant, these two quantities are called inverse proportional quantities, and the relationship between them is called inverse proportional relationship. If the letters X and Y are used to represent two related quantities, and K is used to represent their inverse ratio, it can be represented by the following sub: xy=k (definite) 1. Ratio and proportion.

Proportion is the proportion of the number of parts in the group to the total number, which is used to reflect the composition or structure of the group.

Proportion is divided into scale and proportion. Two expressions with equal ratios are called proportions. Judging whether two ratios can form a proportion depends on whether their ratios are equal. The four numbers that make up a proportion are called proportional terms. 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. In proportion, the product of two external terms is equal to the product of two internal terms. The unknown term of finding proportion is called solution ratio. For example: x: 3 = 9: 27

Solution x: 3 = 9: 27

Solution: 27x=3×9

27x=27

x= 1

Here is a math problem, try to do it!

125%:7=4:x

125%x=4x7

1.25x =28

x =28/ 1.25

x =22.5

⑦ Proportion has the following characteristics

If a:b=c:d(b.d≠0), then there is.

1) ad=bc

2) b:a=d:c (communication ≠0)

3)a:c = b:d； C: A = D: B.

4) (a+b):b=(c+d):d

5) a:(a+b)=c:(c+d) ( a+b≠0，c+d≠0)

6)(a-b):(a+b)=(c-d):(c+d)(a+b≠0，c+d≠0)

The proof process is as follows

Let a:b=c:d=k,

* a:b = c:d

∴a=bk； c=dk

1)∴ad=bk*d=kbd； bc=b*dk=kbd

∴ad=bc

2) Obviously B: A = D: C =1/k.

3)a:c = bk:dk = b:d； Binding attribute 2 is c: a = d: b.

4)∫a:b = c:d

∴(a/b)+ 1=(c/d)+ 1

∴(a+b)/b=(c+d)/d= 1+k； That is, (a+b): b = (c+d): d.

When a+b ≠ 0 and c+d ≠ 0, the binding property 2 has b:(a+b)=d:(c+d).

And b/(a+b) = d/(c+d) =1/(k+1). ...

5)∫b/(a+b)= d/(c+d)

∴ 1- b/(a+b)= 1-d/(c+d)= 1- 1/(k+ 1)

∴ a/(a+b) = c/(c+d) = k/k+1... ② that is, a:(a+b)=c:(c+d).

When A+B ≠ 0 and C+D ≠ 0, the binding property 2 has (a+b): a = (c+d): c.

6) ②-①. Subtract both sides of the equation at the same time to get (a-b)/(a+b) = (c-d)/(c+d) = (k-1)/(k+1).

7) Do this problem: a rectangle with a ratio of 2: 3. The area of this rectangle is 36 square centimeters. Find its length and width.

Please sit in the back row if you are interested. )

Assuming that the width of the rectangle is 2 and the length is 3, then:

Width: 2x2=4 Length: 3x3=9

A: The length of a rectangle is 9 and the width is 4.

[Edit this paragraph] Statistics

proportion

Proportion is the proportion of the number of parts in a population to the total number, which usually reflects the composition and structure of the population. Suppose that the number n in the population is divided into k parts, and the number of each part is "N 1, N2 ..., Nk". According to the definition, the sum of the parts is equal to 1, that is,

N 1/N+N2/N+...+Nk/N= 1

Proportion is to replace the values of all parts of the population with the same radix, that is, all of them are based on 1, so that values of different categories can be compared.

The ratio multiplied by 100 is a percentage or percentage, which is calculated by abstracting the base of comparison to 100. It is expressed as%, indicating how many molecules are in every 100 denominator.