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There are 600 literature and art books, two fifths of which are science and technology books, and three fourths of which are story books
600 × 2 / 5 △ 3 / 4 = 320 (this)
There are story books, science and technology books, literature and art books in the book corner. Story books account for two fifths of the total. Science and technology books account for three fourths of literature and art books. Literature and art books are 20 less than story books. How many books are there?
If the number of story books accounts for 2 / 5 of the total number, then the number of science and technology books and literature and art books accounts for 1-2 / 5 of the total number = 3 / 5; science and technology books: literature and art books = 3:4, literature and art books account for 4 / (3 + 4) = 4 / 7 of the total number of science and technology books and literature and art books; literature and art books account for 4 / 7 × 3 / 5 of the total number = 12 / 35; total number = 20 △ (2 / 5-12 / 35) = 20 × (2 / 35) = 350 a: there are 350 books in the library
There are 50-100 books on the shelf, of which 20% are science and technology books and 1 / 7 are story books. How many are science and technology books and story books on the shelf?
20%=1/5
So the total number of books should be a multiple of 5 and 7
Between 50 and 100, only 70 is a multiple of 5 and 7
There are 70 books
Science and technology books: 70 × 20% = 14
Story books: 70 × 1 / 7 = 10
A: there are 14 science and technology books and 10 story books
The country with the largest land area in the world is - the smallest is - and the country with the least population is -
The country with the largest land area in the world is Russia
The Vatican, the smallest country in the world, is located in Italy
The most populous country in the world is the Vatican, which has only 10000 people
On Coulomb's law
When a charged body cannot be regarded as a point charge, is the force between them larger or smaller than that calculated by Coulomb's law?
For example: the charge quantity of two spheres with radius R is Q1 and Q2 respectively. When the distance between the two spheres is 3R, the electrostatic force of the interaction is?
A.F=kq1q2/9R^2
B.F>kq1q2/9R^2
C.F
B because the two charged bodies have the same amount of different charges, and the charges attract each other, the distribution of the charges on the two balls is not uniform, and they will concentrate on the opposite side, so the distance between the charges is smaller than 3R
What day is teacher's day in 2011? How to calculate
From 2010 teacher's day to 2011 teacher's Day is exactly a year, because 2011 is an ordinary year, so there are 365 days
365 / 7 = 52 1 (day)
So 2011 teacher's Day is the day of the week, as long as the day of the week in 2010 to push back on the line
Teacher's day in 2011 is Saturday
Examples of using mathematics knowledge to solve life problems in junior high school
1. Measure the height of the tree with a tape measure
Standing in front of the tree, one knows the height of the person, the shadow length of the person and the shadow length of the tree, and calculates the height of the tree in proportion to the parallel line
2. Calculate the volume and surface area of irregular parts with the learned calculation formula of regular objects such as cylinder and cone
3. Measure the angle of irregular parts with a protractor to see if they are qualified products
4. Calculate the productivity, percentage of production, etc
77,99,91,80.
What does this string of numbers mean
77 get 99 help 91 you don't know 80 sorry
A comprehensive practical activity group from class 6, Grade 7 went to supermarket a and B to investigate the sales situation during the May Day Festival last year and this year. The following dialogue is the communication between Xiao Kai and two other students after the investigation. According to their dialogue, please calculate the sales of supermarket a and supermarket B during the May Day Festival this year
Xiao Kai: the total sales of the two supermarkets were 1.5 million yuan last year and 1.7 million yuan this year
Xiao Hong: the sales volume of supermarket a is 15% higher than that of last year
Xiaomi: the sales volume of supermarket B is 10% higher than that of last year
You use the equation,
Suppose last year's 51st section a sales x 10000 yuan, then B sales 1.5-x 10000 yuan, this year's 51st section a sales 115 million yuan, B sales 1.1 * (150-x) or 170-115 million yuan, the equation is as follows:
1.15X+1.1*(150-X)=170
1.15X+1.1*(150-X)=170
1.15X+165-1.1X=170
0.05X=5
X=100
1.15X=1.15*100=115；
170-115=55
13,39,52. Greatest common factor,
13=13
39=3*13
52=2*2*13
Greatest common factor 13
RELATED INFORMATIONS
- 1. There are some books on Xiaoming's bookshelf. The number of books ranges from 100 to 150. Among them, 15 are story books, 17 are science and technology books, and most of them are on the bookshelf______ This is a book
- 2. There are some books on Xiaoming's bookshelf. The number of books ranges from 100 to 150. Among them, 15 are story books, 17 are science and technology books, and most of them are on the bookshelf______ This is a book
- 3. There are 3200 popular science books in the school library, accounting for two fifths of all books. The number of story books is 25% less than popular science books How many story books are there in the library?
- 4. There are 3600 books in the library of science and technology, 1 / 6 of which are comic books, 2 / 5 of which are story books, and the rest are science and technology books 3600 × 2 / 5 3600 × (1 / 6 + 2 / 5) 3600 × (2 / 5-1 / 6) 3600 × (1-6 / 1-5 / 2) 3600 × (1-1 / 6)
- 5. There are 800 story books in the library. The number of science and technology books is 58 of story books and 25 of comic books. How many comic books are there?
- 6. A kind of children's story book was delivered to the bookstore. It sold 30% on the first day, and 120% on the second day, 30 more than the first day. How many of these story books were delivered to the bookstore?
- 7. A kind of children's story book was delivered to the bookstore, which sold 30% in the first day, sold 120% in the second day, and bought 30 more in the first day. How many children's story books were delivered to the bookstore What's the point
- 8. The bookstore brought in a batch of story books. On the first day, they sold one package less than one sixth of these books. At this time, there are still seven eighths left unsold. How many packages of these story books have been sold
- 9. A batch of story books were delivered to the bookstore. On the first day, they sold 15 bags less than one sixth of these books, and there were still seven eighths left. How many bags are there in this batch of story books? What's sold 1－7/8=1/8 At the same time, it's 15 bags less than 1 / 6 therefore What are the characteristics of these storybooks 15 (1 / 6-1 / 8) = 360 (packet) why divide by 15?
- 10. I bought 150 story books and a batch of science and technology books. The number of science and technology books is 25 less than 1.2 times of story books. How many science and technology books did the school buy?
- 11. It is known that the vertex P of parabola y = x? + 4x + C is on the line y = 3x + 5
- 12. The story of scientists and inventors in their childhood
- 13. The story of the inventor
- 14. The ratio of story books to literature books is 4:5, and story books are () percent less than literature books
- 15. There are 3600 science and technology books and story books in the school, of which 80% are science and technology books. How many are science and technology books and story books?
- 16. The number of science and technology books is 16% less than that of storybooks. What's the percentage of science and technology books?
- 17. If 400 science and technology books are replaced by story books, the number of story books is three times that of science and technology books. If 100 story books are replaced by science and technology books, the number of story books is 5 / 11 of science and technology books? It's better not to make equations Other solutions to write a good formula to explain the meaning!
- 18. Father chooses books 1. Summarize the full text in concise language What is the profound meaning of "be a man, not a floating grass, but a fisherman on the water" What is the purpose of the passage What's the use of the dash in paragraph 6 5 compare the differences between the father in this article and the father in back
- 19. Xiaohong has to rush to the school of 1000 meters every day. One day, Xiaohong starts at the speed of 80 meters per minute. Xiaohong's father Xiao Hong's father found that she had forgotten to bring her math book, so he immediately chased Xiao Hong at the speed of 180 m / min and caught up with her on the way. Do you know how far away is he from school when he chased Xiao Hong? On the process
- 20. Xiaohong's home is 800 meters away from school. Xiaohong goes to school at the speed of 62 meters per minute in the morning. Six minutes later, Xiaohong's father finds that she has forgotten to bring her pencil case So, Dad immediately at the speed of 155 M / min to catch up, and on the way to catch up. How long did it take dad to catch up with Xiaohong? This is Xiaohong how many meters away from school? Equation!