Solve math problems, solve math problems

This is an invariant question.

The books on the upper floor account for 2 5 of the total number of books on the upper and lower floors of the shelf, then the books on the lower floor account for 1-2 5 = 3 5 of the total number of books on the upper and lower floors of the bookshelf, after increasing 48 books, the books on the lower floor account for 3 4 of the total number of books, and the total number is invariant at this time, so 48 (3 4-3 5) = 320 books, 320 * 2 5 = 128 books.

2.The ratio of the original number of college students in the east and west villages is 4 3, and this year there are 8 people in the east village who are admitted to university, so if the west village is admitted to 3 * 8 4 = 6 people, the west village is still 3 4 in the east village, but the west village is less than 6-5 = 1 people, it is only 5 7 in the east village, so 1 person is now 3 4-5 7 in the east village, then the east village now has 1 (3 4-5 7) = 28 people, the original 28-8 = 20 people, and the west village is 20 * 3 4 = 15 people.

The upper shelves originally contained 128 books.

There are students in the East Village: (8-5*(7 5)) ((7 5)*(3 4)-1) = 20 students.

There are 20*3 4=15 students in the West Village.

3 4-3 5 = 3 20 (Explanation: Originally, the upper layer accounted for 2 5, the lower layer accounted for 3 5, 48 books were taken from the upper layer and put into the lower layer, and the lower layer accounted for 3 4, because no matter how you took it, the total number of books did not change, so these 48 books were 3 20 of the total);

48 (3 20) = 320 books, which is the total number of books;

The original books on the upper layer are 2 5 * 320 = 128.

The number of people in the East Village increased by 8 and the number in the West Village increased by 5, for a total increase of 13 people.

If the total number of people in the original village is y, and the total number of people after the increase is y+13, the original east village is 4y 7, and the original west village is 3y 7, then: After the increase: (4y 7+8):

3y 7+5) = 7:5, find y = 70, that is, there are 70 people in the original 70 people, then there are 40 people in the original east village and 30 people in the original west village.

1 Let the total number of books be x

The original number of the lower layers is (1-2 5)x = 3 5x48 = (3 4-3 5)x

x = 320

The original number of the upper layer is 2 5x = 128

2 There were x in the east village, and there were 3x 4 people in the west village, and there were:

x+8):(3x/4+5)=7:5;

5x+40=21x/4+35;

x/4=5;

x=20;So there were originally 20 people in the East Village, and 15 people in the West Village.

The volume of fertilizer of the same weight must be the same, then the volume after modification is 5 4 times before the modification, because the height of the argument is unchanged is 96cm, so the bottom area becomes larger than the original 5 4 times, the bottom area is only the macro lack formula is r 2, unchanged, only r can be changed.

So the square of the radius becomes 5 4

r^2=900*5/4=1125

r=cm. Now the circumference of the woven bag is 2 r=cm.

Now the woven bag circumferentially increases the length by centimeters.

Let the radius of the later woven bag be r

r^2=50÷｛40÷[π60/2）^2x96]｝÷96÷π=50x900÷40=1125

r = centi, liquid rice, withered.

Now woven bag circumference = 2 r = cm.

Now the circumference of the woven bag has been increased.

1) Solution: Set the number of people in group A to send 30 square meters to clean the ground is x, then:

360/x-300/x=2x=30

A b: The average cleaning of the floor per teacher and student in the two groups is 10.12 square meters.

2) Three. a:300,b:300;

a:301,b:299;

a:302,b:298;

1) The average cleaning floor of each teacher and student in Group A is 10 square meters; b. The average cleaning of the floor per teacher and student in the two groups is 12 square meters each;

2) Three. a:300,b:300;

a:301,b:299;

a:302,b:298;

Solution: If the number of people in group A who is sent to clean 30 square meters of the ground is x, then:

360/x-300/x=2x=30

A b: The average cleaning of the floor per teacher and student in the two groups is 10.12 square meters.

Solution: Let the two stations of A and B be separated by S kilometers.

s-40) 40=[(s-30)+40] [s-40)+30]: s=90

A: The distance between the two stations is 90 kilometers.

If A needs x hours to complete alone, then B needs x to 3 hours to complete alone.

There is the following formula. 1 x + 1 (x-3) Lakaikong = 1 2

Count it yourself, it's too late for me to get off work.