1. There is a difference of 20 books between science and technology books and literature and art books in the book corner of Class One, Grade Five. There are twice as many literature and art books as there are science and technology books. How many books are there respectively?

Science and technology books: 20/(2- 1)=20.

Literature books: 20*2=40.

2. The side length of a square is one meter, and 100 such squares are arranged in sequence for one afternoon to form a rectangle. What is the circumference of this rectangle?

The length of this rectangle is: 100a, the width is a, and the circumference is: (100a+a)*2=202a.

Note:/is a division symbol * is a multiplication symbol.