Fill in the blanks

Use letters to indicate the following quantities.

1. The library has X books and bought 240. There are () books in the library now.

2. Each book is RMB X, and Xiaoming bought 6 books, and the amount payable is RMB ().

The weight of apple is one kilogram, and the weight of pear is three times that of apple. Then, 3a stands for ().

4, A minus B, the difference is 8, A is A and B is ().

5. The circumference of a square with a side length of b cm is () cm and the area is () cm.

6. The train travels 78.5 kilometers per hour and () kilometers per hour.

7. Say the meaning of each formula.

(1) Students in Class One do a math problem A every day, denoted by 7a.

(2) Grade four students subscribe to China Youth Daily 120, which is x more than grade five, 120-x indicates. China Youth Daily costs one yuan each, 120a, (120-x) a) a.

(3) The side length of a square is one centimeter, denoted by 4a and denoted by a2.

(4) Teacher Zhang bought three volleyballs, each at X yuan, and paid the salesman 245 yuan, 245 -3x.

8、0.9∶0.6=9∶( )

9. If y=5x, then x and y are proportional to ().

10 1/2:3/4 The simplest integer ratio is ().

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