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A school logistics staff to a stationery shop to buy test stationery bags for ninth grade students, stationery shop rules a purchase of more than 400, can enjoy a 20% discount. If you buy a ninth grade students, can not enjoy a 20% discount, need to pay 1936 yuan; if you buy 88, can enjoy a 20% discount, also only need to pay 1936 yuan. How many ninth grade students in the school ？
Suppose there are X students in Grade 9. According to the meaning of the question, the equation is: 1936x × 0.8 = 1936x + 88, the equation is: 0.8 (x + 88) = x, the solution is: x = 352, x = 352 is the solution of the original equation. A: there are 352 students in Grade 9 in this school
Xiaoming goes to a stationery store to buy Stationery. If the stationery with a purchase price of 4 yuan is sold after 70% discount, the boss can still get 5%, then the original price of the stationery is - -
Come on
Suppose the original price is X
0.7X-4=0.05*4
0.7X=4.2
X = 4.2 divided by 0.7
X=6
The price is six yuan
A stationery shop bought a batch of new desk lamps. If they were sold at the price of 15 yuan for each kind of desk lamp, 30 lamps could be sold every day. If the price was increased by 1 yuan, the daily sales would be reduced by 2 lamps. In order to make the sales revenue of these desk lamps more than 400 yuan per day, how should we make the sales price of these desk lamps?
To be specific, we should learn the lesson of inequality
The relationship between sales price X and sales revenue y is as follows:
y=x * {30-2(x-15)}
y>400
x{30-2(x-15)} >400
20>x>10
The number of regularly arranged columns: 2, 4, 6, 8, 10, 12 Each term of it is represented by the formula 2n (n is a positive integer). The number of regularly arranged columns: 1, - 2, 3, - 4, 5, - 6, 7, - 8 (1) What formula do you think can be used to express each term of it; (2) what is the 100th number of it? (3) Is 2006 the number in this column? If so, what is the number?
(1) Each term can be expressed by the formula (- 1) n + 1n (n is a positive integer). (2) its 100th number is - 100. (3) 2006 is not the number in this column, because the even numbers in this column are all negative. When n is odd, it means n. when n is even, it means - n
Find the value of n-order determinant | x-a a... A | a x-a... A | a | a a... x-a |
|x-a a ...a|
|a x-a ...a|
|............|
|a a ...x-a|
x-a a………… a
a x-a……… a
……………………
a a………… x-a
r1+r2+…… +The results are as follows
x+(n-1)a x+(n-1)a …… x+(n-1)a
a x-a …… a
……………………………………
a a …… x-a
The first line extracts x + (n-1) a to get
1 1 …… one
a x-a …… a
……………………………………
a a …… x-a
r2-ar1…… And rn-ar1
1 1 …… one
0 x-2a …… 0
……………………………………
0 0 …… x-2a
So determinant = [x + (n-1) a] (x-2a) ^ (n-1)
What is the basis for solving the equation of one variable and one degree to get rid of the denominator
The basis for solving the equation of one variable and one degree to remove the denominator is as follows:
If both sides of the equation are multiplied by the same number (or formula) which is not zero, the equation still holds
The following is the seventh number in the 200th row of a string of numbers arranged in a "tower" shape
What is it
∵ the number form of each group is () 1 / (), ∵ the first number of each line is + 1, so the seventh is - 1. The first line has one number, the second line has two numbers, so the 200 line has 200 numbers. Because the number after / is in accordance with 1.2.3 So there are 199 lines before line 200, that is, (1 + 199) x199 / 2 = n (you can calculate it yourself), so the number after / of the last number in line 199 is n, and the seventh number in line 200 is (+) 1 / (n + 7 = x)
Benefit It's your brain that can't understand, OTZ
The final answer is 19907
The product of a negative integer with an absolute value less than 4 plus a nonnegative integer with an absolute value less than 3 is______ .
Please call the website
Summary of mathematics knowledge in Volume 1 of junior high school
The PEP version should be shorter
The first volume of junior high school mathematics knowledge
Chapter one rational numbers
Positive number, negative number, rational number, opposite number, scientific notation, approximate number
Number axis: use the number axis to represent the number
Absolute value: the absolute value of a positive number is itself; the absolute value of a negative number is its opposite; the absolute value of zero is zero
4 Comparison of positive and negative numbers: positive number is greater than zero, zero is greater than negative number, positive number is greater than negative number, negative number with larger absolute value is smaller
The addition rule of rational numbers
Add two numbers with the same sign, take the same sign, and add the absolute value;
If the absolute value is not equal, add two numbers with different signs, take the sign of the addend with larger absolute value, and subtract the reduced absolute value from the larger absolute value;
Two numbers that are opposite to each other add up to zero;
If you add zero to a number, you still get the number
Subtraction of rational numbers (converting subtraction to addition)
Subtracting a number is equal to adding the opposite of the number
The multiplication rule of rational numbers
When two numbers are multiplied, the same sign is positive, the different sign is negative, and the absolute value is multiplied;
Any number multiplied by zero gets zero
The product is the reciprocal of two numbers of one
Division of 8 rational numbers (converted to multiplication)
Dividing by a nonzero number is equal to multiplying by the reciprocal of the number
The power of 9 rational numbers
Any power of a positive number is a positive number;
Any power of zero is negative;
The odd power of a negative number is negative, and the even power of a negative number is positive
10 mixed operation sequence
(1) First, multiply and divide, then add and subtract;
(2) The same level operation is carried out from left to right;
(3) If there are brackets, first do the operation in brackets, in accordance with the small brackets, brackets, braces in turn
Chapter 2 addition and subtraction of integral
Integral: a general term for monomials and polynomials;
Addition and subtraction of integral 2
(1) Merge congeners
(2) Remove brackets
The third chapter is one variable linear equation
The understanding of 1-dimensional linear equation
The properties of 2-equality
If the same number or formula is added or subtracted from both sides of the equation, the results are still equal;
Both sides of the equation multiply the same number, or divide by the same nonzero number, the results are still equal
3. Solving linear equation of one variable
General steps: remove denominator, remove bracket, move item, merge similar item, coefficient into one
The fourth chapter is a preliminary understanding of graphics
Geometry: plan and solid
2 points, lines, surfaces and bodies
Line, ray and line segment
Two points determine a straight line;
Between two points, the line segment is the shortest
4 jiao
The measure degree of angle
Comparison and operation of angles
Complement and complement: complement and complement of equal angle are equal
There are 12 red, yellow, blue and white balls of the same size in the box. If you want to find out there must be 2 balls of the same color, at least () balls should be touched
If you want to find out that there must be four of the same color, at least () balls should be touched
X-Y = 0 (x.y is not 0), X and Y ()
A. in proportion B. in inverse proportion C. out of proportion
2. When designing a new watch, the technicians of the watch factory want to enlarge the parts of the watch to 50 times of the original. The scale used in drawing should be ()
A．1:50 B．50:1 C．1：500000
3. For a rectangular piece of land, the ratio of length to width is 5:3. If it is drawn on a drawing according to the ratio of 1:80, the ratio of length to width is ()
A．1:80 B．5:3 C．5:240
There are 12 red, yellow, blue and white balls of the same size in the box. If you want to find out there must be 2 balls of the same color, at least 5 balls
If you want to find out that there must be four of the same color, you need to touch at least 13 balls
C & nbsp; & nbsp; out of proportion
B 50：1
B 5：3
I'm glad to answer for you;
RELATED INFORMATIONS
- 1. Xiaoying and several students went to the stationery store to buy exercise books. The stationery store stipulated that if the purchase reached a certain quantity, they could buy them at the wholesale price. So they gathered together 60 yuan to buy them at the wholesale price. In this way, the number of exercise books purchased was 30 more than that purchased at the retail price. If the wholesale price of each exercise book was 45 times of the retail price, what was the retail price of each exercise book How much is it?
- 2. A supermarket used 80000 yuan to purchase a batch of "T-shirts" from other places. Due to the good sales, the supermarket urgently allocated 176000 yuan to purchase "T-shirts" which are twice as much as the last time. However, the second purchase price is 4 yuan more than the first purchase price. The supermarket sells them at 58 yuan per piece, and the remaining 150 pieces are sold out at a 20% discount. How much money has the supermarket made in this business (including two purchases)?
- 3. Every day, the supermarket bought back a batch of T-shirts from other places with 50000 yuan. Due to the good sales, the mall urgently allocated 186000 yuan to buy back T-shirts that were twice as much as the first time. However, the second time was 12 yuan more expensive than the first time. The mall sold them at the price of 80 yuan. In order to shorten the inventory time, the last 400 T-shirts were sold out at a discount of 6.5% How much is the profit of the Communist Party of China?
- 4. In order to promote a product priced at M yuan, supermarket a, supermarket B and supermarket C cut prices by 20% twice in a row, 40% at a time in supermarket B, 30% at the first time in supermarket C and 10% at the second time. At this time, the most cost-effective supermarket for customers to buy this product is () A. A B. B C. C D. B or C
- 5. In order to promote a commodity with the same price, supermarket a, supermarket B and supermarket C cut prices by 20% twice in a row, 40% at a time in supermarket B, 30% at the first time in supermarket C and 10% at the second time. Which supermarket is more cost-effective for customers to buy this commodity A. B. B. C. C. D
- 6. I bought a pen, notebook, stationery and schoolbag in the mall
- 7. The stationery store bought 100 pens at the price of 4 yuan each, and each pen was sold at 6 yuan. When some pens were sold, the remaining pens were sold at a 10% discount. When all pens were sold, the store made a total profit of 188 yuan. How many pens were sold at a 10% discount? Don't use the equation, but use the formula
- 8. Buy 3 pens in a stationery shop and get 2 free pens, 4 yuan each. How much should I pay for 12 pens?
- 9. The school plans to buy 40 pens and some notebooks (the number of notebooks exceeds the number of pens). The price of both a and B plus the stationery shop is 10 yuan for each pen and the number of notebooks It's 2 yuan per book. The preferential way of shop a is 10% off for pens and 20% off for notebooks. Shop B's preferential way is to give one notebook for every five pens. Pens are not discounted, and notebooks are 7.5% off. So how to buy more cost-effective (please see the title and come back) good bonus points
- 10. The stationery store bought 18 boxes of stationery today, including 540 pens and 840 erasers. If the number of erasers in each box is the same as that of pens, how many erasers are there?
- 11. Xiao Ming and Xiao Gang collect digital cards. Xiao Ming's cards account for 16 / 11 of the total. If he gives 15 cards to Xiao Gang, they will have the same number. How many cards do they have in total?
- 12. At the school sports meeting, in the 200m sprint, Xiaoqiang took 2 / 3 minutes, Xiaogang took 50 seconds and Xiaoming took 0.6 minutes. Which of them is the fastest?
- 13. It took Xiaoming 18 seconds to run 100 meters and Xiaogang 24 seconds to run 150 meters. Who runs fast? process
- 14. Xiao Gang and Xiao Ming are in the 100 meter race. When Xiao Gang runs 80 meters, Xiao Ming is 40 meters away from the end. Then when Xiao Gang runs to the end, how many meters is Xiao Ming away from the end?
- 15. The mathematics interest group held a test. There were 15 questions in the whole paper. It was stipulated that 8 points would be deducted for each right question and 4 points would be deducted for each wrong question. Xiaoying got 72 points in total, and she did it right______ Question
- 16. The mathematics interest group held a test. There were 15 questions in the whole paper. It was stipulated that 8 points would be deducted for each right question and 4 points would be deducted for each wrong question. Xiaoying got 72 points in total, and she did it right______ Question
- 17. Xiao Ming went to school from home. After walking at the speed of 50 meters per minute for two minutes, he found that he would be 8 minutes late if he walked at this speed Xiao Ming went to school from home. He walked at a speed of 50 meters per minute for two minutes. He found that he would be 8 minutes late if he walked at this speed. So he accelerated his pace and walked 10 meters more per minute. As a result, when he got to school, he had five minutes to go. What's the distance between Xiao Ming's home and school?
- 18. When Xiao Ming reads a book, the number of pages he has read is 32 of the number of unread pages. When he reads another 30 pages, the number of pages he has read is 73 of the number of unread pages. How many pages are there in this book?
- 19. Help me solve a math problem and answer it in a minute! When Li Mengmeng read a book, he read one third of the whole book on the first day, and 18 pages more than 25% of the whole book on the second day. At this time, the ratio of the number of pages read to the number of pages not read is 3:1. (1) how many pages are there in the book? (we can't use equations to solve it, we must use equations) (2) how many pages did he read the next day?
- 20. The circumference of a cuboid is 80cm, and the ratio of length to width is 4:1. What's the area of the cuboid? Tao Jie and Jiang Tao travel from a to B at the same time, and their speed ratio is 4:3. Tao Jie travels 20 kilometers per hour, and Jiang Tao travels how many kilometers per hour?