There are 420 science and technology books in the library, 2 less than literature and art books 5. How many literature and art books are there in the school library?

420÷（1-2
5）
=420÷3
Five
=700 (copies)
A: there are 700 literature and art books

There are 495 science and technology books in the school library, 47 more than two times the number of literature and art books. How many literature and art books are there

Set up x literary and artistic books and X literary and artistic books
495-47=2x 2x+47=495
448 = 2x, x = 224
x =224
A: 224 literature and art books (495-47) divided by 2
=448 divided by 2
=224 copies (divided by can not be typed, write division sign when writing
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There are 272 science fiction books and comic books in the school library. The number of science fiction books is three times that of comic books. How many science fiction books and comic books are there? Using equation solution

Let x comic books and science fiction books be 3x, x + 3x = 272, x = 63, 3x = 189

There are three kinds of books in the school library. There are 100 comic books known, and literature and art books are 2 5. More comic books than science books How many books are there in total?

Number of literary books:
100×（1-2
5），
=100×3
5，
=60 copies;
Number of science and technology books:
100÷（1+1
4），
=100×4
5，
=80 (copies);
The total of the three books:
100 + 60 + 80 = 240 (Ben);
A: there are 240 books in all

Among the new books bought by the library, story books account for one sixth, comic books and literature books account for three to four. There are 400 literature and art books. How many new books are there in total

Comics 400 △ 4x3 = 300 copies
A total of (300 + 400) / (1-1 / 6) = 840 new books

The number ratio of science and technology books to comic books in the school library is 5:2. The number of comic books is 90 less than that of science and technology books. How many books are there in total?

This is a simple proportional distribution. Compared with comic books, science and technology books are 3 copies less (5-2) and 90 copies less than comic books. We can see that there are 30 copies per copy. There are 7 copies (5 + 2), 30 copies each, and there are 210 copies in total
5-2=3
90 / 3 = 30 copies
5+2=7
7 * 30 = 210 copies
A: a total of 210 comic books and science books

The ratio of the number of technical and comic books in the school library is 5:2. The number of comic books is 90 less than that of science and technology books. How many are there in each? 5-2 = 3; 90 / 3 = 30 Science and technology book: 30 times 5 = 150 (copies) Comic: 30 times 2 = 60 (copies) A: there are 150 science and technology books and 60 comic books Checking calculation: 150-60 = 90 (copies) Why do you do this?

If there are 5 sci-tech books and 2 comic books, then there are 5-2 = 3 more sci-tech books than comic books. If the extra 3 copies are 90 copies, then each copy is 90 / 3 = 30 copies
So there are five science and technology books, which are 5x30 = 150
There are two comic books in total, which are 2x30 = 60

Science and technology books in school library are 30% less than literature and art books, and literature and art books are several percent more than science and technology books

So the science and technology book is 70-1%
There are more literary books than scientific books
30%÷70%≈42.9%

There are 44 science and art books in the school library. If one tenth of the science and technology books are lent out, the ratio of the number of science and technology books to Literature and art books is 3:4 How many science and technology books?

Solution: if there are x science and technology books, then 44-x literature and art books
[x×(1-1/10)]:(44-x)=3:4
4×9/10x=3×(44-x)
18/5x=132-3x
18/5x+3x=132
x=132÷33/5
x=20