When it comes to junior high school math problems, help 20

Suppose he buys x books with a unit price of 8 yuan, and a notebook with a unit price of y yuan, then there are.

8x+(105-x)*12+y=1500-418y=4x-178

And because y is an integer less than 10.

So y can only be $2 or $6.

Solution: (1) Let the extracurricular books with a unit price of yuan be x, and get: 8x+12(105-x)=1500-418, (2 points).

Solution: x=not in question) (3 points).

Because x cannot be a decimal in this problem, Mr. Wang said that he must have made a mistake; (4 points) 2) Set the unit price of the extracurricular book as the yuan as y, and set the unit price of the notebook as the b yuan, according to the title:

0 1500-[8x+12(105-x)+418] 10, (6 points) The solution obtains: 0 4x-178 10, i.e., (7 points) x should be 45 or 46

When x = 45 books, b = 1500 - [8 45 + 12 (105-45) + 418] = 2, when x = 46 books, b = 1500 - [8 46 + 12 (105-46) + 418] = 6, that is: the unit price of the notebook may be 2 yuan or 6 yuan (8 points).

Suppose the two books are x, y and the notebook is z x+y=105 8x+12y+z=1500-418, and we get 4y+z=242

Assuming y=60, z=2 y=59, z=6 y=58, z=10, the notebook may be two-dollar or six-dollar.

Let the unit price of 8 yuan have x books, and the unit price of the notebook is y, according to the title: 8x+12(105-x)+y=1500-418

Simplification: 1260-4x+y=1084, y=4x-178, and because x and y are both positive integers, and y<10, from the above conditions according to y=4x-178 can be deduced:

1.When x=45, y=2,2When x=46, y=6, so the unit price of the notebook may be 2 yuan or 6 yuan.

Solution: Let's say you need at least x kg of wheat.

x(1-15%)=425

x = 500 A: A minimum of 500 kg of wheat is required.

Set at least x kg of wheat is required.

x(1-15%)=425

Solution x=500

According to the above rule, the number at the beginning of each line is the line number of the line, that is, the first line starts with 1, the second line starts with 2, and the 200th line starts with 200.

The number macro group of each row is added by 1 in turn, and the number of modules in the row is 2*n-1, that is, ., then the 200th line has 200*2-1=399 masking oranges.

The first number in line 200 is 200, and the 401st number is 200 + 399-1 = 598

Therefore, the sum of line 200 is (200+598)*399 2=399 2=159201

I think it's an interesting finding that this sum is exactly the square of the number in the bank.

The hundredth fierce annihilation should be; The number of bends should be 2n-1, and it is 399, so it is.

200+201+..598, (200 + 201) + (liquid 202 + 598) * (397 2).

The 200th line has a total of 2 * 200-1 = 399 numbers, and the elimination is Na Danzi Chi You: 200 + 201 + 202 + .598