Elementary school math problems, call for help. I wrote it after the question just now, and I asked

If it's 3 21, it's 1 7

The rest of the book, 1 7 of *** is 1 3 of the storybook

Everyone adds 12 books, and it does not affect the difference between the books, so the difference is the same as the original: (7 3-1) = 4 3 The remaining storybooks = 48, so the remaining storybooks are 36, and the remaining *** is 84, add back 12, that is, the storybooks 48, ***96

Set ***x book.

The storybook is X-48

3 2*(x-12)=3 1(x-48-12)It looks like you have a problem with the question.

It turns out to be a negative number.

Solution: If *** is x, then the storybook is (x-48).

From the meaning of the title, it can be seen:

3 21(x-12)=1 3(x-48-12) gives x=96

So *** there are 96 copies.

Set the storybook x***x+48

x-12）/3=（x+48-12）/7

Because 3 21 is 1 7.

Storybook = 48

***=96

Let *** be x, and know from the inscription [x-12]*3 21=[x-48-12]*1 3

The solution is x=114

Solution: If there are ***x books, then the storybook is x-48 copies. The column equation gives x-12) 3 21=(x-48-12) 1 3 and gives x=96

So *** there are 96 copies.

If you set ***x, then the storybook is x-48

The formulas that can be listed are as follows:

3 21*(x-12)=1 3*(x-48-12) finally gives x=96

Let the storybook be a, *** is a+48, (a+48-12)*21 3=(a-12)*1 3

Circumference = (196-16*4) 2 = 132 2 = 66 cm.

Assuming that the length and width are x,y respectively, then: 4x+4y+16*4=196, so x+y=33

The perimeter of the rectangle is known, and the area is largest only when length=width=33 2=, but since it can only be taken as an integer.

When the length = 16 and width = 17, the area is the largest, and the area = 16 * 17 = 272 cm.

The circumference is 30, part of which is 10 and 20

In 2 cases, (10-3) cm or (20-3) cm are removed from point B

So the answer is 7 or 17

2.Suppose there are x books for storybooks and y books for science and technology, and the system of equations is derived from the problem, x-1 13 x = y-7

x+y=207

The solution yields x= , y=

ps: It seems that the solution is not an integer, the title is correct, it should be like this.

3.Let B originally have x kilograms, which is derived from the meaning of the question, 5:x+5=1:7, and the solution is x=30

1 66 and 2 3

2 Solution: Storybook x Science and Technology Book 207-x (1-1 13) x = 207-x - 7 x = 104 207-104 = 103

Answer: 104 storybooks 103 science and technology books 3 set B bucket has x kilograms.

5: (x+5)=1:7 x=30 Answer: There are 30 kg 4 solution x days.

600 5)x=80*30 x=20 A.

5 1920*4%=Yuan Answer...

6 1 (1 10+1 10*5 6)=60 11=5 and 5 11 (days) Answer: . .

The amount of water in the reservoir must be evenly poured into the reservoir, 5 pumps can be drained for 20 consecutive days, 6 same pumps can be drained for 15 consecutive days, if you want to drain in 6 days, how many same pumps are needed?

15 units are required.

Let the uniform water volume be m and the current water volume of the reservoir is a, and the following equations can be listed as 20m+a=20*5

15m+a=15*6

The solution yields a=60 m=2

The number of pumping machines required for 6 days is n, and the equation is 60+2n=6*n

Find n=15

So 15 pumps are needed, and they can be pumped in 6 days.

Thank you for adopting.

Let there be a and enter b every day, then.

a+20b) (5*20)=(a+15b) (6*15) The solution gives a=30b

Another 6 days of draining requires x sets of the same pump.

Then (a+20b) (5*20)=(a+6b) 6x solution x=12

A: 12 sets of the same pumping machine can be drained in 6 days.

Solution: Let the raw water be stored as a daily water inlet b a pumping machine pumping water a day x 6 drain to Y from the above formula.

a+20b-100x=0

a+15b-90x=0

a+6b-xy=0

Get: y=72

15 pumping machines are required, and they can be pumped in 6 days.

The salary ratio of A and B is 3:1, so A's salary is 3 times that of B.

Because B's salary is 300 yuan.

So A's salary = 3 * 300 = 900

The salary ratio of B and C is 1:5, so C's salary is 5 times that of B.

Because B's salary is 300 yuan.

So C's salary is 300*5=1500

A: B = 3:1, then A's salary is 300*3=900

C: B = 5:1, then C's salary is 300 * 5 = 1500

A's salary is three times that of B, so it is 300*3=900, and C is five times that of B, so it is 300*5=1500. I hope you are satisfied.

The salary ratio of A, B, and C is 3:1:5, so A has 3 copies, B 1 share, C 2 copies, B 300 yuan A is 300 divided by 1 times 3 equals 900, and C is 300 divided by 1 times 5 equals 1500

It is known that (x-3) is a factor of kx 2+10x-192, so a root of kx 2+10x-192=0 is x=3, so 9k+30-192=0, so k=18

Happy studying.