1. Because the total number of people is fixed, the number of rows is inversely proportional to the number of people in each row.

Let the number of rows be m.

Then m: 18 = 20: 24.

M = 18 * 20/24 = 15 (line)

To stop at line 12, the number of people per line is set to n.

n:20 = 18: 12

N = 20 * 18/12 = 30 (person)

Two. 48*9/ 16=27

This is for 27 yuan.

III.30 * 6/5 = 36

Sail 36 kilometers per hour

Four. 3000×2.5÷2.4=3 125 pieces

Now you can make 3 125 pieces of clothes.

Solution: It takes X days to complete the construction of this highway.

400:4=800:x

400 times =4×800

x=3200÷400

x=8

It will take another eight days

Intransitive verb 1.5-0.3= 1.2 ton

Solution: Now this batch of coal can burn for X days.

1.5: 1.2=X:40

Solution: 1.2X=40× 1.5.

X=60÷ 1.2

X=50

It can burn for fifty days.

Page 25

I. Positive and Inverse Proportions

2. Solution: It is assumed that 1000 pieces are produced every day and completed in X days.

Then you can know the meaning of the question.

1000X=750*20

solve

X= 15 days.

It will be finished in fifteen days.

3. solution: suppose it takes x days.

7500:X=3000:4

3000X=7500×4

3000X=30000

X=30000÷3000

X= 10 A: it takes 10 days.

Solution: 8 tons of soybeans can extract X tons of oil.

8:X= 100: 15

100X=8* 15

X= 1.2 A: 8 tons of soybean can squeeze out 1.2 tons of oil.

5. Solution: There are X female employees.

72:x=(5+3):3

72:x= 8:3

8x =72×3

x=72×3÷8

x=27

A: There are 27 female employees.

6. Assuming that the goods can be delivered within X days,

3:600=X:( 160* 12)，

600x=3*( 160* 12)

x=9.6

It will be delivered in 9.6 days.