There are 30 literature books, 25 story books, 45 science and technology books, and 2500 story books. How many books are there in the library How many books are there in science and technology books and literature and art books? How many more books are science and technology books than literature and art books? How many less books are story books than literature and art books Grade 6 of primary school

There are 30 literature books, 25 story books, 45 science and technology books, and 2500 story books. How many books are there in the library How many books are there in science and technology books and literature and art books? How many more books are science and technology books than literature and art books? How many less books are story books than literature and art books Grade 6 of primary school

There are 30 books on literature and art, 25 books on stories and 45 books on science and technology. There are 2500 books on stories. There are 10000 books on these three categories in the library. There are 4500 books on science and technology and 3000 books on literature and art,
Science and technology books are more than literature books (4500-3000) / 3000 = 50%
Story books are less than literature books (3000-2500) / 3000 = 16.667%

There are 320 science and technology books, story books, literature and art books on average. Science and technology books account for 4 / 5 of story books, and story books account for 6 / 7 of literature and art books

If there are x literature and art books, there are 6 / 7X story books and 4 / 5 * 6 / 7X science and technology books
x+6/7x+4/5*6/7x=320*3
The process is like this, but the result is not an integer. Maybe you have the wrong number

There are 94 story books, science and technology books and literature and art books in the library. Three seventh of science and technology books are equal to one third of literature and art books. There are 30 stories. How many are science and technology books and literature and art books?

Science and technology book (94-30) / (1 + 3 / 7 / 1 / 3)
=64÷（1+9/7）
=64÷16/7
=28 copies
Literature and art books 94-30-28 = 36

What's the season in China when the earth is closest to the sun

Winter
At the beginning of January every year, about January 3, the earth is closest to the sun, about 147.1 million kilometers away. It is the perihelion of the earth, and it is winter in China

A practical problem in junior high school solved by equation
Xiao Ming made up a question: the seven dates from Monday to Sunday are arranged in a row. The sum of the seven numbers is 210. What's the date of Sunday? Can Xiao Hua answer it? Why?

Xiaohua can't solve it, because: let the first day of the seven dates in this line be x day, then they are x + 1, x + 2, x + 3, x + 4, x + 5, x + 6 in turn, and we get x + X + 1 + X + 2 + X + 3 + X + 4 + X + 5 + X + 6 = 210, x = 27x + 1 = 28, x + 2 = 29, x + 3 = 30, x + 4 = 31, x + 5 = 32, x + 6 = 33, the maximum date of each month is 31, 33 > 31, so we can't

A square with a circumference of 16 cm is cut along the diagonal to form a parallelogram. What is the area of the parallelogram?

The area of parallelogram is equal to square (16 △ 4) &# 178; = 16 cm & # 178;

103 × 12, 20 × 55, 24 × 205 are calculated by the law of multiplicative distribution

103*12=(100+3)*12=1200+36=1236
20*55=20*(50+5)=1000+100=1100
24*205=24*(200+5)=4800+120=4920

Reduction of COS square (π / 4 - α) + cos square (π / 4 + α)

The original formula = (COS π / 4cos α + sin π / 4sin α) & sup2; + (COS π / 4cos α - sin π / 4sin α) & sup2; = (√ 2 / 2cos α + √ 2 / 2Sin α) & sup2; + (√ 2 / 2cos α - √ 2 / 2Sin α) & sup2; = 1 / 2 (COS & sup2; α + 2cos α - sin α + Sin & sup2; α) + 1 / 2 (COS & sup2; α - 2

Judge right or wrong; 1 / 8 of 7m is as long as 7 / 8 of 1m

Same length
7X1/8=1X7/8

7.5 △ 9 / 2 = what is the ratio

7.5 △ 9 / 2 = 5:3 = 5 / 3